Periods

The horizontal rows on the periodic table

All elements in the same period have the same number of energy levels in their electron cloud

Groups

The vertical columns on the periodic table

All elements in the same group have the same number of valence electrons

Electron Clouds

​Electron clouds are broken down into shells or energy levels, that each hold a certain number of e-

• Level 1 (closest to the nucleus): holds a max of 2 e-

• Level 2: holds up to 8 e-

• Level 3: holds up to 8 e- (for our purposes)

• Level 4: holds up to 18 e- (for our purposes)