What is the difference between valence, valence electrons, and a valence shell?
Valence electrons are indeed the electrons found in the outer shell of an atom. This outer shell is refered to as the valence shell. The valence of an atom, however, is it’s bonding capacity. For example: Carbon has 4 valence electrons, 4 unpaired electrons, and a valence of 4. Hydrogen has 1 valence electron, 1 unpaired electron, and a valence of 1. Oxygen has 6 valence electrons, 2 unpaired electrons, and a valence of 2. Nitrogen has 5 valence electrons, 3 unpaired electrons, and a valence of 3. Phosphorus also has 5 valence electrons and 3 unpaired electrons. However, in the phosphate ion it is actually exhibiting a valence of 5 since it forms a total of five bonds with four molecules of oxygen. The important take home message is simply that hydrogen tends to form 1 bond, oxygen 2, nitrogen 3, carbon 4, and phosphorus, in the phosphate ion, 5.
