Key Concepts and Summary
Valence electronic structures can be visualized by drawing Lewis symbols (for atoms and monatomic ions) and Lewis structures (for molecules and polyatomic ions). Lone pairs, unpaired electrons, and single, double, or triple bonds are used to indicate where the valence electrons are located around each atom in a Lewis structure.
Most structures—especially those containing second row elements—obey the octet rule, in which every atom (except H) is surrounded by eight electrons. Exceptions to the octet rule occur for odd-electron molecules (free radicals), electron-deficient molecules, and hypervalent molecules.
covalent bond in which two pairs of electrons are shared between two atoms
molecule that contains an odd number of electrons
diagram showing lone pairs and bonding pairs of electrons in a molecule or an ion
symbol for an element or monatomic ion that uses a dot to represent each valence electron in the element or ion
two (a pair of) valence electrons that are not used to form a covalent bond
guideline that states main group atoms will form structures in which eight valence electrons interact with each nucleus, counting bonding electrons as interacting with both atoms connected by the bond
bond in which a single pair of electrons is shared between two atoms
bond in which three pairs of electrons are shared between two atoms