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What Is an Element in Chemistry?
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by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
A chemical element is a substance that cannot be broken down by chemical means. Although elements aren't changed by chemical reactions, new elements may be formed by nuclear reactions.
Elements are defined by the number of protons they possess. Atoms of an element all have the same number of protons, but they can have different numbers of electrons and neutrons. Changing the ratio of electrons to protons creates ions, while changing the number of neutrons form isotopes.
There are 118 known elements. Research is underway to make element 120. When element 120 is made and verified, the periodic table will need to be changed to accommodate it!
Key Takeaways: Chemical Element Definition
A chemical element is a substance that cannot be further broken down by any chemical reaction.
Each element has a unique number of protons in its atom. For example, a hydrogen atom has 1 proton, while a carbon atom has 6 protons.
Varying the number of electrons in an atom of an element produces ions. Changing the number of neutrons produces isotopes.
There are 118 known elements.
Examples of Elements
Any of the types of atoms listed on the periodic table is an example of an element, including:
proton - technically a lone proton qualifies as an example of the element hydrogen
Examples of Substances That Are Not Elements
If more than one type of atom is present, a substance is not an element. Compounds and alloys are not elements. Similarly, groups of electrons and neutrons are not elements. A particle must contain protons to be an example of an element. Non-elements include:
water (composed of hydrogen and oxygen atoms)
brass (composed of multiple types of metal atoms)
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