Review definition of valence electrons and valence shells or energy level.
Review maximum electrons which can be placed into each of the primary quantum level shells.
Use neon as the primary example, show the electron configuration of sodium (one electron greater than neon) and fluorine (one electron less than neon). Indicate that sodium can obtain a stable neon configuration by donating an electron, and fluorine can obtain stability ( reach an octet) by accepting an electron.