There are many ways to predict the properties of an element here's one example.As you move from left to right the electron affinity and ionization energy both increase .Since elements of the same family have similar characteristic,you can often predict the properties of another element in its family
C i think but you should pick it anyway
Excuse me not giving an explanation; I haven't even learned chemistry before. I usually give explanations for math/english.
I think it would be for flourine: 7
aluminum: 8
can't help with the rest...
sorry!