6.1  Ionic Bonding (continued)

Stable Electron Configurations

The highest occupied energy level of a noble gas atom is filled.   When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react. The noble gases have stable electron configurations with eight valence electrons (or two in the case of helium).

The chemical properties of an element depend on the number of valence electrons. Therefore, it is useful to have a model of atoms that focuses only on valence electrons. The models in Figure 2 are electron dot diagrams. An electron dot diagram is a model of an atom in which each dot represents a valence electron. The symbol in the center represents the nucleus and all the other electrons in the atom.

Figure 2  In an electron dot diagram, each dot represents a valence electron.