Predict which of the following ions would be likely to form:?

Question

Br-

Ne-

Ne+

Answer 1

Br-
Ions form because atoms "want" (I used "want" to avoid an extremely long answer) 8 valence (outer shell) electrons (H and He are exceptions). Using the periodic table you can see that Ne is a group 8A element, meaning it has 8 valence electrons already. It won't form ions. Br, however, is group 7A, meaning it has 7 valence electrons. Br will readily accept an electron to form the Br- ion.