Research suggests that crochet probably developed most directly from Chinese needlework, a very ancient form of embroidery known in Turkey, India, Persia and North Africa, which reached Europe in the 1700s and was referred to as tambouring, from the French tambour or drum.
POLAR BONDS. 1) Covalent bond between two atoms with unequal electronegativities results in unequal sharing of electrons. 2) Unequal electron sharing leads to partially positive and partially negative charges on opposite ends of the bond.When the two atoms involved in a covalent bond both have equal affinity for electrons, the electrons in the bond are evenly shared between them.hese types of covalent bonds are called polar bonds because the electron distribution or charge is unevenly distributed or polarized. Partial charges are represented by lower case delta (+) Î´+ or lower case delta (-) Î´-. A separation of partial charges within a polar covalent bond is referred to as a dipole.
Covalent bonds are a sharing of electrons; an even sharing of electrons results in a nonpolar covalent bond. Nonpolar bonds mostly exist between atoms of the same element. For example, oxygen contains six electrons in its outer shell. To gain a full outer shell of eight electrons, oxygen atoms form double bonds with other oxygen atoms. Because they are identical atoms, they share the four electrons equally. When atoms of two different elements share electrons, they form polar covalent bonds. In polar covalent bonds, the shared electrons spend more of their time near one atom than the other, resulting in an uneven sharing and a partial charge on both atoms in the bond. Water is an example of a polar covalent bond.