how many alkali metals will combine with 1 oxygen family member?

Question

 i don't understand what it asking for?

Answer 1

Examine what it takes to fill the outer shell of O.  The outer shell of O has 6 electrons.  You need 8 to fill that shell.  An alkali metal atom can give 1 electron, so it takes 2 alkali metal atoms to fill the outer shell of O.  Hence 2 alkali metal atoms combine with one O atom.