Reading Groups and Periods

Valence electrons are the electrons in the outermost shell of an atom that are involved in forming bonds with other atoms.

Barium (Ba) has 2 valence electrons.

The period indicates the number of energy levels (electron shells) that the elements in that row possess.

Beryllium (Be) is in group 2, period 2.

Helium (He) is in group 18, period 1.

Alkali metals are the elements in group 1 of the periodic table, characterized by having one valence electron.

Cesium (Cs) is an alkali metal with 6 electron shells.

The atomic number of Argon (Ar) is 18.

The group of an element is determined by the number of valence electrons it has.

The period number corresponds to the number of electron shells an atom has.