who came up with the model of the atom
List of Dutch discoveries


work on isomers of German chemist Johannes Wislicenus, and showed that the four valencies of the carbon atom were probably directed in space toward the four corners of a regular tetrahedron, a model which explained how optical activity could be associated with an asymmetric carbon atom. He shares credit for this with the French chemist Joseph Le Bel, who independently came up with the same idea. Three months before his doctoral degree was awarded Van 't Hoff published this theory, which today is regarded as the foundation of stereochemistry, first in a
452700
Drude model


(and hence is also known as the Drude–Lorentz model) and is a classical model. Later it was supplemented with the results of quantum theory in 1933 by Arnold Sommerfeld and Hans Bethe, leading to the Drude–Sommerfeld model. The Drude model considers the metal to be formed of a mass of positively charged ions from which a number of "free electrons" were detached. These may be thought to have become delocalized when the valence levels of the atom came in contact with the potential of the other atoms.
6770030
Robert James Moon


him to reconsider the usual interpretation of the Rutherford scattering data, which ignores the variation in force between charged particles as a result of relative velocities and accelerations. Calculations based on the Weber electrodynamics forced Moon to re-conceptualize most of what is, still today, taken for granted in atomic and nuclear physics. In the 19841986 period, Moon came up with his proposal for a geometric ordering of protons and neutrons in the atomic nucleus based on nested Platonic solids. This "Moon Model", was inspired by Johannes Kepler’s
1521064
Bohr model


the strongest X-ray line emitted by atoms under electron bombardment (then known as the K-alpha line), and their atomic number . Moseley's empiric formula was found to be derivable from Rydberg and Bohr's formula (Moseley actually mentions only Ernest Rutherford and Antonius Van den Broek in terms of models). The two additional assumptions that [1] this X-ray line came from a transition between energy levels with quantum numbers 1 and 2, and [2], that the atomic number when used in
4613778
Alpha particle


its center, making the positive charge dense enough to deflect any positively charged alpha particles that came close to what was later termed the nucleus. Prior to this discovery, it was not known that alpha particles were themselves atomic nuclei, nor was the existence of protons or neutrons known. After this discovery, J.J. Thomson's "plum pudding" model was abandoned, and Rutherford's experiment led to the Bohr model (named for Niels Bohr) and later the modern wave-mechanical model of the atom. Rutherford went on to
19333109
Bohr model


using Heisenberg's matrix mechanics. The current picture of the hydrogen atom is based on the atomic orbitals of wave mechanics which Erwin Schrödinger developed in 1926. However, this is not to say that the Bohr-Sommerfeld model was without its successes. Calculations based on the Bohr–Sommerfeld model were able to accurately explain a number of more complex atomic spectral effects. For example, up to first-order perturbations, the Bohr model and quantum mechanics make the same predictions for the spectral line splitting in the Stark effect. At
4613790
SMILES arbitrary target specification


. As originally defined by Daylight, the codice_1 descriptor is used to specify ring membership. In the Daylight model for cyclic systems, the smallest set of smallest rings (SSSR) is used as a basis for ring membership. For example, indole is perceived as a 5-membered ring fused with a 6-membered ring rather than a 9-membered ring. The two carbon atoms that make up the ring fusion would match codice_24 and the other carbon atoms would match codice_25. The SSSR model has been criticised by OpenEye who, in their implementation of
816434
Atomic Rooster


support the album. In June 1971, just before they began configuring their line-up once again, the single "Devil's Answer" hit No. 4 in the UK. Atomic Rooster began recording "In Hearing of Atomic Rooster" (UK No. 18). Crane felt the band needed a singer who could "project" to an audience, and asked Leaf Hound vocalist Pete French to audition for the band. Not long after French came into the studio, Du Cann began to feel increasingly marginalised, having
5677051
Bohr model


In atomic physics, the Rutherford–Bohr model or Bohr model or Bohr diagram, presented by Niels Bohr and Ernest Rutherford in 1913, is a system consisting of a small, dense nucleus surrounded by revolving electrons —similar to the structure of the Solar System, but with attraction provided by electrostatic forces rather than gravity. After the cubic model (1902), the plum-pudding model (1904), the Saturnian model (1904), and the Rutherford model (1911) came the "Rutherford–Bohr model"
4613746
Rutherford model


physical model for subatomic structure, as an interpretation for the unexpected experimental results. In it, the atom is made up of a central charge (this is the modern atomic nucleus, though Rutherford did not use the term "nucleus" in his paper) surrounded by a cloud of (presumably) orbiting electrons. In this May 1911 paper, Rutherford only committed himself to a small central region of very high positive or negative charge in the atom. For concreteness, consider the passage of a high speed α particle through an
6063646
Vector model of the atom


In physics, in particular quantum mechanics, the vector model of the atom is a model of the atom in terms of angular momentum. It can be considered as the extension of the Rutherford-Bohr-Sommerfeld atom model to multi-electron atoms. The model is a convenient representation of the angular momenta of the electrons in the atom. Angular momentum is always split into orbital L, spin S and total J: Given that in quantum mechanics, angular momentum is quantized and there is an uncertainty relation for the components of
14210580
Vector model of the atom


, formula_17. It can be considered the extension of the Bohr model because Niels Bohr also proposed angular momentum was quantized according to: where "m" is an integer, produced correct results for the Hydrogen atom. Although the Bohr model doesn't apply to multi-electron atoms, it was the first successful quantization of angular momentum applied to the atom, preceding the vector model of the atom. For one-electron atoms (i.e. hydrogen), there is only one set of cones for the orbiting electron. For multi
14210586
Rutherford model


The Rutherford model was devised by Ernest Rutherford to describe an atom. Rutherford directed the Geiger–Marsden experiment in 1909 which suggested, upon Rutherford's 1911 analysis, that J. J. Thomson's plum pudding model of the atom was incorrect. Rutherford's new model for the atom, based on the experimental results, contained new features of a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom and with this central volume also containing the bulk of the atomic mass of the atom. This
6063644
Embedded atom model


In computational chemistry and computational physics, the embedded atom model, embedded-atom method or EAM, is an approximation describing the energy between atoms, an interatomic potential. The energy is a function of a sum of functions of the separation between an atom and its neighbors. In the original model, by Murray Daw and Mike Baskes, the latter functions represent the electron density. EAM is related to the second moment approximation to tight binding theory, also known as the Finnis-Sinclair model. These models are particularly appropriate for
12015670
Atomic whirl


The atomic whirl is the logo of the American Atheists, and has come to be used as a symbol of atheism in general as some American Atheist members claim. The Atomic Whirl is based on the Rutherford model of the atom which is proven wrong, erroneously showing the orbital paths of electrons around the central nucleus, and not on the atomic orbitals which is a near perfect experimental approximation. It resembles the authoritative logos and symbols of the United States Atomic Energy Commission and the International Atomic Energy Agency who also based their designs on
5608177
Geiger–Marsden experiment


at the time of Rutherford's experiment was the "plum pudding model". This model was devised by Lord Kelvin and further developed by J. J. Thomson. Thomson was the scientist who discovered the electron, and that it was a component of every atom. Thomson believed the atom was a sphere of positive charge throughout which the electrons were distributed, a bit like plums in a Christmas pudding. The existence of protons and neutrons was unknown at this time. They knew atoms were very tiny (Rutherford assumed they were in the
14401899
Space-filling model


In chemistry, a space-filling model, also known as a "calotte model", is a type of three-dimensional (3D) molecular model where the atoms are represented by spheres whose radii are proportional to the radii of the atoms and whose center-to-center distances are proportional to the distances between the atomic nuclei, all in the same scale. Atoms of different chemical elements are usually represented by spheres of different colors. Space-filling calotte models are also referred to as CPK models after the chemists
17248977
S-50 (Manhattan Project)


naming) by Lise Meitner and Otto Robert Frisch soon after, opened up the possibility of a nuclear chain reaction with uranium. Fears that a German atomic bomb project would develop nuclear weapons, especially among scientists who were refugees from Nazi Germany and other fascist countries, were expressed in the Einstein-Szilard letter. This prompted preliminary research in the United States in late 1939. Niels Bohr and John Archibald Wheeler applied the liquid drop model of the atomic nucleus to explain the mechanism of nuclear fission. As the experimental physicists studied fission
14596572
Rutherford backscattering spectrometry


a single massive positive particle. This led him to the conclusion that the atom's positive charge could not be diffuse but instead must be concentrated in a single massive core: the atomic nucleus. Calculations indicated that the charge necessary to accomplish this deflection was approximately 100 times the charge of the electron, close to the atomic number of gold. This led to the development of the Rutherford model of the atom in which a positive nucleus made up of "N"e positive particles, or protons, was surrounded by "N" orbiting
7701291
Atomic orbital


visualizing the submicroscopic behavior of electrons in matter. In this model the electron cloud of a multi-electron atom may be seen as being built up (in approximation) in an electron configuration that is a product of simpler hydrogen-like atomic orbitals. The repeating "periodicity" of the blocks of 2, 6, 10, and 14 elements within sections of the periodic table arises naturally from the total number of electrons that occupy a complete set of s, p, d and f atomic orbitals, respectively, although for
861537
Atomic number


table (also known as element number, atomic number, and symbolized "Z"). This proved eventually to be the case. The experimental position improved dramatically after research by Henry Moseley in 1913. Moseley, after discussions with Bohr who was at the same lab (and who had used Van den Broek's hypothesis in his Bohr model of the atom), decided to test Van den Broek's and Bohr's hypothesis directly, by seeing if spectral lines emitted from excited atoms fitted the Bohr theory's postulation that the
71908
Rydberg constant


formula comes from substituting the reduced mass for the mass of the electron. A generalization of the Bohr model describes a hydrogen-like ion; that is, an atom with atomic number "Z" that has only one electron, such as C. In this case, the wavenumbers and photon energies are scaled up by a factor of "Z" in the model. The Rydberg constant is one of the most precisely determined physical constants, with a relative experimental uncertainty of fewer than 7 parts in 10. The ability to measure
20297138
Plum pudding model


The plum pudding model is one of several historical scientific models of the atom. First proposed by J. J. Thomson in 1904 soon after the discovery of the electron, but before the discovery of the atomic nucleus, the model tried to explain two properties of atoms then known: that electrons are negatively-charged particles and that atoms have no net electric charge. The plum pudding model has electrons surrounded by a volume of positive charge, like negatively-charged "plums" embedded in a positively-charged "pudding". In
2598453
Promela


. Note that atomic sequences restrict the amount of interleaving that is allowed in a distributed system. Intractable models can be made tractable by labeling all manipulations of local variables with atomic sequences. Message channels are used to model the transfer of data from one process to another. They are declared either locally or globally, for instance as follows: This declares a buffered channel that can store up to 16 messages of type "short" ("capacity" is 16 here). The statement: sends the value of the expression "
4987680
Bohr model


of the "Shell Model of the Atom" below). This was established empirically before Bohr presented his model. Bohr extended the model of hydrogen to give an approximate model for heavier atoms. This gave a physical picture that reproduced many known atomic properties for the first time. Heavier atoms have more protons in the nucleus, and more electrons to cancel the charge. Bohr's idea was that each discrete orbit could only hold a certain number of electrons. After that orbit is full, the next level would have to be
4613770
Molecular dynamics


of specific atomic orbitals. The matrix is then diagonalized to determine the occupancy of the different atomic orbitals, and empirical formulae are used once again to determine the energy contributions of the orbitals. There are a wide variety of semi-empirical potentials, termed tight-binding potentials, which vary according to the atoms being modeled. Most classical force fields implicitly include the effect of polarizability, e.g., by scaling up the partial charges obtained from quantum chemical calculations. These partial charges are stationary with respect to the mass of the atom
20236286
Sigma-pi and equivalent-orbital models


in the two models. Nevertheless, as pointed out in Carroll's textbook, at lower levels of theory, the two models make different quantitative and qualitative predictions, and there has been considerable debate as to which model is most useful conceptually and pedagogically. Two different explanations for the nature of double and triple covalent bonds in organic molecules were proposed in the 1930s. Linus Pauling proposed that the double bond in ethylene results from two equivalent tetrahedral orbitals from each atom, which later came to be called "banana bonds" or "
15439336
Olefin metathesis


example, propylene (C3) forms in a reaction of 2-butene (C4) with tungsten hexachloride and tetramethyltin (C1). In the same year Pettit who synthesised cyclobutadiene a few years earlier independently came up with a competing mechanism. It consisted of a tetramethylene intermediate with sp hybridized carbon atoms linked to a central metal atom with multiple three-center two-electron bonds. Experimental support offered by Pettit for this mechanism was based on an observed reaction inhibition by carbon monoxide in certain metathesis reactions of 4-nonene with a tungsten metal carbonyl
5649714
Vaught conjecture


2, for example: The idea of the proof of Vaught's theorem is as follows. If there are at most countably many countable models, then there is a smallest one: the atomic model, and a largest one, the saturated model, which are different if there is more than one model. If they are different, the saturated model must realize some "n"-type omitted by the atomic model. Then one can show that an atomic model of the theory of structures realizing this "n"-type (in a language expanded
21040140
Island of stability


with the first usage of the term "superheavy element" in a 1958 paper published alongside Frederick Werner. However, this idea did not attract wide interest until a decade later, after improvements in the nuclear shell model. In this model, the atomic nucleus is built up in "shells", analogous to electron shells in atoms. Independently of each other, neutrons and protons have energy levels that are normally close together, but after a given shell is filled, it takes substantially more energy to start filling the next.
18174726
J. J. Thomson


F and l were known, so m/e could be calculated. As to the source of these particles, Thomson believed they emerged from the molecules of gas in the vicinity of the cathode. Thomson imagined the atom as being made up of these corpuscles orbiting in a sea of positive charge; this was his plum pudding model. This model was later proved incorrect when his student Ernest Rutherford showed that the positive charge is concentrated in the nucleus of the atom. In 1905, Thomson discovered the natural radioactivity of potassium.
20351785
André Dreiding


. It was a so-called skeletal model, which consisted of slim stainless steel tubes and rods. Unlike the older ball-and-stick models, the atoms were not represented by a ball, but rather by the point of intersection of the steel tubes. The intersection area was painted with a color to indicate the identity of the atom. As the tubes represented the bonds, the model focused on the geometry of the bonds between atoms rather than the atoms themselves. The Dreiding Stereomodel was not the first skeletal model
4588244
Stable model semantics


any changes in the definition of a stable model. In this theory of strong negation, we distinguish between atoms of two kinds, "positive" and "negative", and assume that each negative atom is an expression of the form formula_115, where formula_116 is a positive atom. A set of atoms is called "coherent" if it does not contain "complementary" pairs of atoms formula_117. Coherent stable models of a program are identical to its consistent answer sets in the sense of [Gelfond and Lifschitz, 1991]
89674
Infinite divisibility


and these lack determinate values. According to the Standard Model of particle physics, the particles that make up an atom—quarks and electrons—are point particles: they do not take up space. What makes an atom nevertheless take up space is "not" any spatially extended "stuff" that "occupies space", and that might be cut into smaller and smaller pieces, "but" the indeterminacy of its internal spatial relations. Physical space is often regarded as infinitely divisible: it is thought that any region in
13036490
Prout's hypothesis


weight of chlorine, which is 35.45 times that of hydrogen, could not at the time be explained in terms of Prout's hypothesis. Some came up with the ad hoc claim that the basic unit was one-half of a hydrogen atom, but further discrepancies surfaced. This resulted in the hypothesis that one-quarter of a hydrogen atom was the common unit. Although they turned out to be wrong, these conjectures catalyzed further measurement of atomic weights; a great benefit to chemistry. The discrepancy in the atomic weights was
11744696
Permutation model


In mathematical set theory, a permutation model is a model of set theory with atoms (ZFA) constructed using a group of permutations of the atoms. A symmetric model is similar except that it is a model of ZF (without atoms) and is constructed using a group of permutations of a forcing poset. One application is to show the independence of the axiom of choice from the other axioms of ZFA or ZF. Permutation models were introduced by and developed further by . Symmetric models were introduced by Paul Cohen. Suppose that
19312605
Low-energy electron diffraction


other atoms. This must be done in a self-consistent way, since the emitted field of an atom depends on the incident effective field upon it. Once the effective field incident on each atom is determined, the total field emitted from all atoms can be found and its asymptotic value far from the crystal then gives the desired intensities. A common approach in LEED calculations is to describe the scattering potential of the crystal by a "muffin tin" model, where the crystal potential can be imagined being divided up by non
2175949
Rutherford model


Rutherford's paper appeared, the proposal regarding the exact identity of atomic number and nuclear charge "was" made by Antonius van den Broek, and later confirmed experimentally within two years, by Henry Moseley. These are the key indicators- After Rutherford's discovery, scientists started to realize that the atom is not ultimately a single particle, but is made up of far smaller subatomic particles. Subsequent research determined the exact atomic structure which led to Rutherford's gold foil experiment. Scientists eventually discovered that atoms have a positively charged nucleus (
6063651
Coot (software)


fit of a section of atomic model to the electron density in real time, with graphical feedback. The user may also intervene in this process, dragging the atoms into the right places if the initial model is too far away from the corresponding electron density. Tools for general model building: Tools for moving existing atoms: Tools for adding atoms to the model: In macromolecular crystallography, the observed data is often weak and the observation-to-parameter ratio near 1. As a result, it is possible to build an
174662
Atom


the uncertainty principle, formulated by Werner Heisenberg in 1927. In this concept, for a given accuracy in measuring a position one could only obtain a range of probable values for momentum, and vice versa. This model was able to explain observations of atomic behavior that previous models could not, such as certain structural and spectral patterns of atoms larger than hydrogen. Thus, the planetary model of the atom was discarded in favor of one that described atomic orbital zones around the nucleus where a given electron is most likely to be observed
336500
Stable model semantics


no train is approaching. To incorporate strong negation in the theory of stable models, Gelfond and Lifschitz [1991] allowed each of the expressions formula_82, formula_112, formula_46 in a rule to be either an atom or an atom prefixed with the strong negation symbol. Instead of stable models, this generalization uses "answer sets", which may include both atoms and atoms prefixed with strong negation. An alternative approach [Ferraris and Lifschitz, 2005] treats strong negation as a part of an atom, and it does not require
89673
One World or None


the principle of the electron, and German theorist Albert Einstein came up with the theory of relativity. Nuclear physics was a product of New Zealand physicist Ernest Rutherford's work on the atomic nucleus, Danish physicist Niels Bohr's identification of atomic structure and American physicist Carl David Anderson's discovery of the positron. Other advances included English physicist James Chadwick discovering the neutron, while French scientists Irène Joliot-Curie and her husband Frédéric Joliot-Curie studied artificial radioactivity. Further nuclear research was carried out by Enrico Fermi, who transmuted uranium
12214851
Raman cooling


will acquire a velocity formula_13. By repeating this process several times (eight in the original paper, see references), the temperature of the cloud can be lowered to less than a microkelvin. This cooling scheme starts from atoms in a magneto-optical trap. An optical lattice is then ramped up, such that an important fraction of the atoms are trapped. If the lasers of the lattice are powerful enough, each site can be modelled as a harmonic trap. Since the atoms are not in their ground state, they
7460519
Standard Model


, all atoms consist of electrons orbiting around atomic nuclei, ultimately constituted of up and down quarks. Second- and third-generation charged particles, on the other hand, decay with very short half-lives and are observed only in very high-energy environments. Neutrinos of all generations also do not decay and pervade the universe, but rarely interact with baryonic matter. In the Standard Model, gauge bosons are defined as force carriers that mediate the strong, weak, and electromagnetic fundamental interactions. Interactions in physics are the ways
3412254
Vaught conjecture


by finitely many constants) is a third model, not isomorphic to either the atomic or the saturated model. In the example above with 3 models, the atomic model is the one where the sequence is unbounded, the saturated model is the one where the sequence does not converge, and an example of a type not realized by the atomic model is an element greater than all elements of the sequence. The topological Vaught conjecture is the statement that whenever a Polish group acts continuously on a Polish space, there are either countably
21040141
Stable model semantics


atoms. "Head atoms:" If an atom formula_82 belongs to a stable model of a logic program formula_36 then formula_82 is the head of one of the rules of formula_36. "Minimality:" Any stable model of a logic program formula_36 is minimal among the models of formula_36 relative to set inclusion. "The antichain property:" If formula_42 and formula_89 are stable models of the same logic program then formula_42 is not a proper subset of formula_89. In other words, the set of stable models of a program is an
89666
Stable model semantics


ground atoms into three sets: true, false and unknown. If an atom is true in the well-founded model of formula_36 then it belongs to every stable model of formula_36. The converse, generally, does not hold. For instance, the program has two stable models, formula_103 and formula_104. Even though formula_7 belongs to both of them, its value in the well-founded model is "unknown". Furthermore, if an atom is false in the well-founded model of a program then it does not
89669
Toroidal ring model


incidentally calculated both Planck's constant "h" and Boltzmann's constant "k", suggested that something in the "resonators" themselves provided these discrete frequencies. Numerous theories about the structure of the atom developed in the wake of all the new information, of which the 1913 model of Niels Bohr came to predominate. The Bohr model proposed electrons in circular orbit around the nucleus with quantized values of angular momentum. Instead of radiating energy continuously, as classical electrodynamics demanded from an accelerating charge, Bohr's electron radiated discretely when
10369199
DEVS


formula_2 that is the set of non-negative real numbers plus infinity. An atomic DEVS model is defined as a 7-tuple where The atomic DEVS model for player A of Fig. 1 is given Player=formula_16 such that formula_17 Both Player A and Player B are atomic DEVS models. Simply speaking, there are two cases that an atomic DEVS model formula_18 can change its state formula_19: (1) when an external input formula_20 comes into the system formula_18; (2) when the elapsed time formula_22 reaches the lifespan of formula_23
5323021
Rutherford model


surprising finding, as it implied a strong central charge less than 1/3000th of the diameter of the atom. The Rutherford model served to concentrate a great deal of the atom's charge and mass to a very small core, but didn't attribute any structure to the remaining electrons and remaining atomic mass. It did mention the atomic model of Hantaro Nagaoka, in which the electrons are arranged in one or more rings, with the specific metaphorical structure of the stable rings of Saturn. The plum pudding model of J. J. Thomson also
6063648
Keating model


In physics, The Keating Model is a model that theoretical physicist Patrick N. Keating introduced in 1966 to describe forces induced on neighboring atoms when one atom moves in a solid. The term most often applies to the forces on first- and second-nearest neighboring atoms that arise when an atom is moved in tetrahedrally-bonded solids, such as diamond, silicon, germanium, and a number of other covalent crystals with the diamond or zinc blende structures. Crystalline solids generally consist of an ordered array of interconnected atoms, generated by repetition
19282620
Plum pudding model


known: Thomson chose the third possibility as the most likely structure of atoms. Thomson published his proposed model in the March 1904 edition of the "Philosophical Magazine", the leading British science journal of the day. In Thomson's view: ... the atoms of the elements consist of a number of negatively electrified corpuscles enclosed in a sphere of uniform positive electrification, ... With this model, Thomson abandoned his 1890 "nebular atom" hypothesis based on the vortex atomic theory in which atoms were composed of immaterial vortices and suggested that
2598455
Plum pudding model


of gold. Their professor, Ernest Rutherford, expected to find results consistent with Thomson's atomic model. It was not until 1911 that Rutherford correctly interpreted the experiment's results which implied the presence of a very small nucleus of positive charge at the center of gold atoms. This led to the development of the Rutherford model of the atom. Immediately after Rutherford published his results, Antonius Van den Broek made the intuitive proposal that the atomic number of an atom is the total number of units of charge present in its nucleus.
2598459
Chemical bond


electron may form a part of the shell of two different atoms and cannot be said to belong to either one exclusively." That same year, Walther Kossel put forward a theory similar to Lewis' only his model assumed complete transfers of electrons between atoms, and was thus a model of ionic bonding. Both Lewis and Kossel structured their bonding models on that of Abegg's rule (1904). Niels Bohr proposed a model of the atom and a model of the chemical bond. According to his model for a diatomic
6232657
Multiscale modeling


which were used to model large complex chemical systems and reactions. In physics and chemistry, multiscale modeling is aimed to calculation of material properties or system behavior on one level using information or models from different levels. On each level particular approaches are used for description of a system. The following levels are usually distinguished: level of quantum mechanical models (information about electrons is included), level of molecular dynamics models (information about individual atoms is included), coarse-grained models (information about atoms and/or groups of atoms is
9818307
Extended periodic table


quantum mechanical descriptions of atomic structure, the g-block would correspond to elements with partially filled g-orbitals, but spin-orbit coupling effects reduce the validity of the orbital approximation substantially for elements of high atomic number. While Seaborg's version of the extended period had the heavier elements following the pattern set by lighter elements, as it did not take into account relativistic effects, models that take relativistic effects into account do not. Pekka Pyykkö and Burkhard Fricke used computer modeling to calculate the positions of elements up to "
19154568
Ohm's law


have demonstrated that Ohm's law works for silicon wires as small as four atoms wide and one atom high. The dependence of the current density on the applied electric field is essentially quantum mechanical in nature; (see Classical and quantum conductivity.) A qualitative description leading to Ohm's law can be based upon classical mechanics using the Drude model developed by Paul Drude in 1900. The Drude model treats electrons (or other charge carriers) like pinballs bouncing among the ions that make up the structure of the material. Electrons will
4548900
Ball-and-stick model


the bonds, and the distances between the centers of the spheres should be proportional to the distances between the corresponding atomic nuclei. The chemical element of each atom is often indicated by the sphere's color. In a ball-and-stick model, the radius of the spheres is usually much smaller than the rod lengths, in order to provide a clearer view of the atoms and bonds throughout the model. As a consequence, the model does not provide a clear insight about the space occupied by the model. In this
14599812
Close Combat (video game)


for the project, as a real-time wargame, first came when Atomic president Keith Zabalaoui encountered "Dune II". Dr. Steven Silver, a specialist in post-traumatic stress disorder among military veterans, approached the team with his research into state-trait anxiety during this period. He subsequently helped to develop a psychological modeling system for "Project X"s soldiers. Zabalaoui later said that the company's more traditional wargames "never really excited" him as a designer, and he noted that the veterans Atomic had consulted for
9398192
Ernst Mach


all we can know is our sensations and that knowledge should be confined to pure experience. In accordance with empirio-critical philosophy, Mach opposed Ludwig Boltzmann and others who proposed an atomic theory of physics. Since one cannot observe things as small as atoms directly, and since no atomic model at the time was consistent, the atomic hypothesis seemed to Mach to be unwarranted, and perhaps not sufficiently "economical". Mach had a direct influence on the Vienna Circle philosophers and the school of logical positivism in general. To
10593741
Solid-state physics


periodicity of atoms in a crystal — its defining characteristic — facilitates mathematical modeling. Likewise, crystalline materials often have electrical, magnetic, optical, or mechanical properties that can be exploited for engineering purposes. The forces between the atoms in a crystal can take a variety of forms. For example, in a crystal of sodium chloride (common salt), the crystal is made up of ionic sodium and chlorine, and held together with ionic bonds. In others, the atoms share electrons and form covalent bonds. In metals,
14112626
Aufbau principle


the electronic configuration can be built up by placing electrons in the lowest available orbitals until the total number of electrons added is equal to the atomic number. Thus orbitals are filled in the order of increasing energy, using two general rules to help predict electronic configurations: A version of the aufbau principle known as the nuclear shell model is used to predict the configuration of protons and neutrons in an atomic nucleus. In neutral atoms, the approximate order in which subshells are filled is given by the "n + ℓ rule",
17091575
Thomas–Fermi model


distribution of electrons in an atom. Although electrons are distributed nonuniformly in an atom, an approximation was made that the electrons are distributed uniformly in each small volume element "ΔV" (i.e. locally) but the electron density formula_1 can still vary from one small volume element to the next. For a small volume element "ΔV", and for the atom in its ground state, we can fill out a spherical momentum space volume "V"  up to the Fermi momentum "p" , and thus, where formula_3 is
5751197
Intel GMA


found in the Intel Atom N2600 processor and Atom D2500 models. It supports DirectX version 9.0c. Similar to the GMA 3600, but this version is clocked at 640 MHz. It is found in Atom N2800, Atom D2550, Atom D2500, Atom D2600 and Atom D2700 models. It supports DirectX version 9.0c. Protected Audio Video Path (PAVP) restricts the data path within a computer during video playback (e.g., Blu-ray discs). It is supported by newer chipsets (e.g. Intel G45) and operating systems (
4194619
Bohr model of the chemical bond


In addition to the model of the atom, Niels Bohr also proposed a model of the chemical bond. He propose this model first in the article "Systems containing several nuclei" - the third and last of the classic series of articles by Bohr, published in November 1913 in "Philosophical Magazine". According to his model for a diatomic molecule, the electrons of the atoms of the molecule form a rotating ring whose plane is perpendicular to the axis of the molecule and equidistant from the atomic nuclei. The dynamic equilibrium of
13059681
Atomic model (mathematical logic)


In model theory, an atomic model is a model such that the complete type of every tuple is axiomatized by a single formula. Such types are called principal types, and the formulas that axiomatize them are called complete formulas. A complete type "p"("x", ..., "x") is called principal (or atomic) if it is axiomatized by a single formula φ("x", ..., "x") ∈ "p"("x", ..., "x"). A formula φ in a complete theory "
15206832
Atomic theory


may exhibit the properties of both a wave and a particle. For example, it can be refracted like a wave, and has mass like a particle. A consequence of describing electrons as waveforms is that it is mathematically impossible to simultaneously derive the position and momentum of an electron. This became known as the Heisenberg uncertainty principle after the theoretical physicist Werner Heisenberg, who first described it and published it in 1927. This invalidated Bohr's model, with its neat, clearly defined circular orbits. The modern model of the atom
2598496
Melting-point depression


. This feature distinguishes the model, as the other models predict melting of the nanoparticle surface prior to the bulk atoms. If the LDM is true, a solid nanoparticle should function over a greater temperature range than other models predict. The LDM assumes that the surface atoms of a nanoparticle dominate the properties of all atoms in the particle. The cohesive energy of the particle is identical for all atoms in the nanoparticle. The LDM represents the binding energy of a nanoparticles as function of the free energies of the volume and surface.
15496733
Atom


radiation in discrete spectra. Later in the same year Henry Moseley provided additional experimental evidence in favor of Niels Bohr's theory. These results refined Ernest Rutherford's and Antonius Van den Broek's model, which proposed that the atom contains in its nucleus a number of positive nuclear charges that is equal to its (atomic) number in the periodic table. Until these experiments, atomic number was not known to be a physical and experimental quantity. That it is equal to the atomic nuclear charge remains the accepted atomic model today.
336496
Molecular modelling


treating atoms as the smallest individual unit (a molecular mechanics approach), or explicitly modelling protons and neutrons with its quarks, anti-quarks and gluons and electrons with its photons (a quantum chemistry approach). Molecular mechanics is one aspect of molecular modelling, as it involves the use of classical mechanics (Newtonian mechanics) to describe the physical basis behind the models. Molecular models typically describe atoms (nucleus and electrons collectively) as point charges with an associated mass. The interactions between neighbouring atoms are described by spring-
19202324
Tight binding


In solid-state physics, the tight-binding model (or TB model) is an approach to the calculation of electronic band structure using an approximate set of wave functions based upon superposition of wave functions for isolated atoms located at each atomic site. The method is closely related to the LCAO method (linear combination of atomic orbitals method) used in chemistry. Tight-binding models are applied to a wide variety of solids. The model gives good qualitative results in many cases and can be combined with other models that give
21920888
Bohr model


charged nucleus. Given this experimental data, Rutherford naturally considered a planetary-model atom, the Rutherford model of 1911 – electrons orbiting a solar nucleus – however, said planetary-model atom has a technical difficulty. The laws of classical mechanics (i.e. the Larmor formula), predict that the electron will release electromagnetic radiation while orbiting a nucleus. Because the electron would lose energy, it would rapidly spiral inwards, collapsing into the nucleus on a timescale of around 16 picoseconds. This atom model is disastrous, because it predicts
4613750
Fundamental interaction


" or "messenger particles" of underlying fields—interact with matter particles, called fermions. Everyday matter is atoms, composed of three fermion types: up-quarks and down-quarks constituting, as well as electrons orbiting, the atom's nucleus. Atoms interact, form molecules, and manifest further properties through electromagnetic interactions among their electrons absorbing and emitting photons, the electromagnetic field's force carrier, which if unimpeded traverse potentially infinite distance. Electromagnetism's QFT is quantum electrodynamics (QED). The electromagnetic interaction was modelled
10643646
Magnetic structure


to specific atoms, giving atomic spins, which interact only over a short range and typically are analyzed with the Heisenberg model. Here, finite temperatures lead to a deviation of the atomic spins' orientations from the ideal configuration, thus for a ferromagnet also decreasing the macroscopic magnetization. For localized magnetism, many magnetic structures can be described by magnetic space groups, which give a precise accounting for all possible symmetry groups of up/down configurations in a three-dimensional crystal. However, this formalism is unable to account for some
2799975
Keating model


of a unit cell in three dimensions, and are of two extreme types—ionic crystals, and covalent crystals. Others are intermediate: partly ionic and partly covalent. Ionic crystals are made up of quite different ions, such as Na and Cl in common salt, for example, while covalent crystals such as diamond are made up of atoms that share electrons in a covalent bond. In either case, attractive and repulsive forces resist moving an atom/ion or a set of them from their equilibrium positions, thus giving solids
19282621
Atomic theory


's model they were not stationary). Thomson's plum pudding model was disproved in 1909 by one of his former students, Ernest Rutherford, who discovered that most of the mass and positive charge of an atom is concentrated in a very small fraction of its volume, which he assumed to be at the very center. In the Geiger–Marsden experiment, Hans Geiger and Ernest Marsden (colleagues of Rutherford working at his behest) shot alpha particles at thin sheets of metal and measured their deflection through the use of a fluorescent
2598483
Hantaro Nagaoka


the structure of the atom. The recent discovery by J. J. Thomson of the negatively charged electron implied that a neutral atom must also contain an opposite positive charge. In 1903, Thomson had suggested that the atom was a sphere of uniform positive electrification, with electrons scattered through it like plums in a pudding, giving rise to the term plum pudding model. Nagaoka rejected Thomson's model on the grounds that opposite charges are impenetrable. In 1904, Nagaoka proposed an alternative planetary model of the atom in which a positively charged center
10861164
Plum pudding model


this model, atoms were known to consist of negatively charged electrons. Though Thomson called them "corpuscles", they were more commonly called "electrons" which G. J. Stoney proposed as the "fundamental unit quantity of electricity" in 1891. At the time, atoms were known to have no net electric charge. To account for this, Thomson knew atoms must also have a source of positive charge to balance the negative charge of the electrons. He considered three plausible models that would be consistent with the properties of atoms then
2598454
Atomic coffee machine


flathead) and B (Roundhead) had a black and white circular Atomic badge. As for the Isomac "La splendida", it wore a black sticker Atomic cappuccino which was applied on both white and red models. In Austria, Desider Stern applied the trademark on various models stating with the 102, 104, 105 and 110 and extending to the 402E series. The inventions related to the Model 105, 110 and 402E were patented by Desider Stern. The Qualital company in Hungary produced another range of Atomic trademarked machines,
4593154
Introduction to quantum mechanics


is quantized. Understanding exactly what this property was, and why it was quantized, was a major part in the development of quantum mechanics, as shown in the rest of this article. [[File:Bohr atom model English.svg|thumb|The [[Bohr model]] of the atom, showing an electron transitioning from one orbit to another by emitting a photon]] In 1913 [[Niels Bohr]] proposed [[Bohr model|a new model of the atom]] that included quantized electron orbits: electrons still orbit the nucleus
21080811
Stable model semantics


belong to any of its stable models. Thus the well-founded model of a logic program provides a lower bound on the intersection of its stable models and an upper bound on their union. From the perspective of knowledge representation, a set of ground atoms can be thought of as a description of a complete state of knowledge: the atoms that belong to the set are known to be true, and the atoms that do not belong to the set are known to be false. A possibly "incomplete" state of knowledge
89670
Stable model semantics


. For instance, the program has two stable models, formula_122 and formula_123. The first model is coherent; the second is not, because it contains both the atom formula_124 and the atom formula_125. According to [Gelfond and Lifschitz, 1991], the closed world assumption for a predicate formula_1 can be expressed by the rule (the relation formula_1 does not hold for a tuple formula_129 if there is no evidence that it does). For instance, the stable model of the program consists of 2 positive atoms and 14 negative
89675
Homology modeling


the modeling assessment experiment CASP is known as the global distance test (GDT) and measures the total number of atoms whose distance from the model to the experimental structure lies under a certain distance cutoff. Both methods can be used for any subset of atoms in the structure, but are often applied to only the alpha carbon or protein backbone atoms to minimize the noise created by poorly modeled side chain rotameric states, which most modeling methods are not optimized to predict. Several large-scale benchmarking efforts have been made to assess the
11566952
Nuclear chemistry


did the Geiger–Marsden experiment (gold foil experiment) which showed that the 'plum pudding model' of the atom was wrong. In the plum pudding model, proposed by J. J. Thomson in 1904, the atom is composed of electrons surrounded by a 'cloud' of positive charge to balance the electrons' negative charge. To Rutherford, the gold foil experiment implied that the positive charge was confined to a very small nucleus leading first to the Rutherford model, and eventually to the Bohr model of the atom, where
10954734
Bohr model


of symplectic manifolds which can be quantized. In particular, the symplectic form should be the curvature form of a connection of a Hermitian line bundle, which is called a prequantization. Niels Bohr proposed a model of the atom and a model of the chemical bond. According to his model for a diatomic molecule, the electrons of the atoms of the molecule form a rotating ring whose plane is perpendicular to the axis of the molecule and equidistant from the atomic nuclei. The dynamic equilibrium of the molecular system is achieved through the balance
4613792
Space-filling model


Linus Pauling described accurate scale models of molecules which they had built at Caltech. In their models, they envisioned the surface of the molecule as being determined by the van der Waals radius of each atom of the molecule, and crafted atoms as hardwood spheres of diameter proportional to each atom's van der Waals radius, in the scale 1 inch = 1 Å. To allow bonds between atoms a portion of each sphere was cut away to create a pair of matching flat faces, with the cuts dimensioned so that the distance between sphere
17248982
Nirvana (software)


a Global Name Space across three of infoGROUP’s computer operations centers in the Omaha area. In 2012, General Atomics released Nirvana version 4.3. In 2014, General Atomics changed the Nirvana business model from a large government contract, fee for service model, to a standard commercial software model. In 2015, General Atomics initiated a strategic relationship with Pixit Media/ArcaStream in the United Kingdom, integrating Nirvana with Pixit Media and ArcaStream’s products. In 2016, General Atomics released Nirvana version 5.0. In May 2018, probes of
17587561
Acer Aspire One


Acer Aspire One is a line of netbooks first released in July 2008 by Acer Inc. Many characteristics of a particular model of Acer Aspire One are dictated by the CPU platform chosen. Initial models were based on the Intel Atoms. Later, models with various AMD chips were introduced. Newer versions of the Atom were adopted as well. Early versions were based on the Intel Atom platform, which consists of the Intel Atom processor, Intel 945GSE Express chipset and Intel 82801GBM (ICH7M) I/O controller, and is available
18470195
Hydrogen-bridged cations


fast-equilibrating system in which a hydrogen atom rapidly shifts between two adjacent carbon atoms. In this model, fast equilibrium results from a low energy barrier between the two conformations of the molecule, and each conformer has a localized positive charge. The potential energy diagram of this model is characterized by a double-well with two energy minima. The non-classical view (Figure 1.b) involves the delocalization of two electrons over three atoms (1 hydrogen and 2 carbon atoms). The model is characterized by a 3-membered ring
3364364
Coot (software)


University of California at Santa Cruz), and Eugene Krissinel (Daresbury Laboratory). Coot can be used to read files containing 3D atomic coordinate models of macromolecular structures in a number of formats, including pdb, mmcif, and Shelx files. The model may then be rotated in 3D and viewed from any viewpoint. The atomic model is represented by default using a stick-model, with vectors representing chemical bonds. The two halves of each bond are coloured according to the element of the atom at that end of the bond
174659
Hubbard model


" orbital, which can either be spin up (formula_1) or spin down (formula_2). This orbital can be occupied by at most two electrons, one with spin up and one down (see Pauli exclusion principle). Now, consider a 1D chain of hydrogen atoms. Under band theory, we would expect the 1s orbital to form a continuous band, which would be exactly half-full. The 1D chain of hydrogen atoms is thus predicted to be a conductor under conventional band theory. But now consider the
12670701
Covalent radius of fluorine


it is bonded to, giving the bonds a certain amount of sigma bond character. In addition, the fluorine atom also receives a certain amount of pi electron density back from the central atom giving rise to double bond character through (p-p)π or (p-d)π "back bonding". Thus, this model suggests that the observed shortening of the lengths of bonds is due to these double bond characteristics. Reed and Schleyer, who were skeptical of Pauling’s proposition, suggested another model in 1990. They determined that
19152687
Paul Peter Ewald


Ewald met Ella Philippson, who was to become his wife. In the spring of 1913, Niels Bohr, of the Institute for Theoretical Physics at the University of Copenhagen, submitted his theory of the Bohr atomic model for publication. Later that year, Ewald attended the Birmingham meeting of the British Association where he heard accounts and discussions of James Jeans’ review on radiation theory and Bohr’s model. This ignited a major new area of research for Sommerfeld and his students – the study and interpretation of atomic spectra and molecular band
4701163
The Big Reunion


who previously insisted that Katona would be excluded from any Atomic Kitten reunion, was unable to take part in the show due to her pregnancy. Honeyz's reformation came in the form of a third different line-up that consisted of founding members Célena Cherry and Heavenli Denton, and Mariama Goodman, who replaced Denton when she initially left the group in 1999, and vice versa when Goodman herself departed in 2000. Original member Naima Belkhiati decided not to take part in the reunion, so Cherry called up Goodman as her replacement.
5842995
Discovery of the neutron


result, by Bohr's later account, not only established atomic number as a measurable experimental quantity, but gave it a physical meaning as the positive charge on the atomic nucleus. The elements could be ordered in the periodic system in order of atomic number, rather than atomic weight. The result tied together the organization of the periodic table, the Bohr model for the atom, and Rutherford's model for alpha scattering from nuclei. It was cited by Rutherford, Bohr, and others as a critical advance in understanding the nature
10645980
Deterministic simulation


each other and with manned individual entity simulators to support training, combat development experiments, and test of evaluation studies. Taylor Enterprise Dynamics is an objectoriented software system used to model, simulate, visualize, and monitor dynamic-flow process activities and systems. With Taylor ED’s open architecture, software users can access standard libraries of atoms to build models. Atoms are Taylor ED’s smart objects and model building resources. In addition to Taylor ED’s standard atom libraries, users can create new atoms themselves. Performance evaluation of highly
21161807
Geiger–Marsden experiment


, positively charged particle of matter. According to Thomson's model, if an alpha particle were to collide with an atom, it would just fly straight through, its path being deflected by at most a fraction of a degree. At the atomic scale, the concept of "solid matter" is meaningless, so the alpha particle would not bounce off the atom like a marble. It would be affected only by the atom's electric fields, and Thomson's model predicted that the electric fields in an atom are too weak
14401901
Atomic physics


of the periodic system of elements by Mendeleev was another great step forward. The true beginning of atomic physics is marked by the discovery of spectral lines and attempts to describe the phenomenon, most notably by Joseph von Fraunhofer. The study of these lines led to the Bohr atom model and to the birth of quantum mechanics. In seeking to explain atomic spectra an entirely new mathematical model of matter was revealed. As far as atoms and their electron shells were concerned, not only did this yield a better overall description, i.e. the
861377
Molecular model


determining crystal structures, many laboratories built models based on spheres. With the development of plastic or polystyrene balls it is now easy to create such models. The concept of the chemical bond as a direct link between atoms can be modelled by linking balls (atoms) with sticks/rods (bonds). This has been extremely popular and is still widely used today. Initially atoms were made of spherical wooden balls with specially drilled holes for rods. Thus carbon can be represented as a sphere with four holes at the tetrahedral angles
21269798
Molecular model


by a coordination sphere of electronegative atoms (e.g. PO tetrahedra, TiO octahedra). Structures can be modelled by gluing together polyhedra made of paper or plastic. A good example of composite models is the Nicholson approach, widely used from the late 1970s for building models of biological macromolecules. The components are primarily amino acids and nucleic acids with preformed residues representing groups of atoms. Many of these atoms are directly moulded into the template, and fit together by pushing plastic stubs into small holes. The plastic grips well and makes bonds
21269804