Hw problem 2A.15

[aphung1E]

How do you solve this ? Is there a certain rule you have to follow?
2A.15 Write the most likely charge for the ions formed by each of
the following elements: (a) S; (b) Te; (c) Rb; (d) Ga; (e) Cd.

[Kavya Immadisetty 2B]

Elements are generally likely to try and form an octet with the valence electrons (exceptions include H, Li, Be, and B who want to create a duplet). So S needs 2 electrons to form a full valence shell so the most likely ion is S^2-. Te is also 2 electrons so it will form Te^2-. Rb is 1 electron away from having a full valence shell so it's likely to form Rb⁺. Ga is 3 electron away from having a full valence shell so it's likely to form Ga³⁺. Cd's valence shell just includes the 5s-electrons so it will lose those 2 to form Cd²⁺.