http://img525.imageshack.us/img525/2290/84419342em1.th.gif [Broken] in case A: S has a bigger electonegative energy then Ca so it will "take" 2 electrons from Ca inorder to be a complete gas like (Ar) so i know why there is +2 on Ca and -2 on S . Ca has after perfect gas 4S^2 S =[Ne]3s^2 3P^4 but there are dots and cols what they mean?? regarding B: for Br to become a perfect gas like(Kr) it needs to take only one electron why there is -2 ?? and what are all the dots nere it and cols ??