Question

how can you tell whether an atom will form a+ or - ion?

Answer 1

It (most often) depends whether it's situated on the periodic table. The first 2 columns/periods (e.g. Na, Mg) lose electrons and thus become positively charged (cations). Group 6 and 7 gain e, and become negatively charged (anions). A lot of elements can do both (gain and lose) so it depends what they're interacting with.

Answer 2

if an atom looses or gives away its electrons its has -ve ion
bt if the atom gains or receives electrons then its a +ve ion

Answer 3

You said it the opposite way, rane.

Answer 4

ops sorry