The number of valence electrons=increases from the left to right across a period.
The number of valence electrons=stay the same from the top to the bottom of a group.
Electrons are added into the outermost=s orbital in Groups 1 and 2.
Electrons are added in the outermost=d orbital in Groups 3 through 12.
Electrons are added in the outermost=p orbital in Groups 13 through 18.
