Answer:
they should have a number that can completely transfer and fill the other atom
Explanation:
example:
sodium(2.8.1)and Chlorine(2.8.7)the sodium will give chlorine the 1 valence electrobo so they both become stable(2.8)±and(2.8.8)–
magnesium(2.8.2)and oxygen(2.6)same way as above to abtain mg(2.8)±²and oxygen(2.8)–²
