How do I tell if atoms need to gain/lose electrons?

Question

If so, how many?

Answer 1

elements are always trying to become like the noble gases...(the ones with 8 valence electrons, at the last column in the reference table) so, if an element has, say, 6 valence electrons, it would want to gain 2 to obtain 8. If an element has, for example, 2 valence electrons, it would want to lose 2 to return to 8 from its other ring.