How Many Covalent Bonds Can These Elements Form?

[Soilwork]

Homework Statement

Determine the number of covalent bonds that are possible for atoms of the following elements: silicon, bromine, nitrogen, sulphur and neon

The Attempt at a Solution

OK so I know that you can find the number of possible covalent bonds by considering the electron configuration of these elements. So since you know the number of valence electrons you can determine the number of possible bonds.

From this I get 4, 1, 3, 2 and 0 (in order).

Now if you consider the valencies of the ions $$B^-, N^3^-, S^2^-$$ you will end up with the same number of possible covalent bonds. However, I didn't think that you could use the valencies of ions because aren't ions just atoms that have lost or gained electrons. I mean I swear you can have $$O^-, O^2^-$$ ions. Which ion valence would you use then?

So am I wrong? Can you actually use the valence of ions to determine the number of possible covalent bonds as well as the electron configuration of the element?

 

[Astronuc]

You are more or less right because the ion valence is indicative of the number of electrons needed to completely fill the p-suborbital.

See second plate at - http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html

http://www.webelements.com/

Group 13 (3A) can form 3 covalent compounds (sharing 3 electrons)
Group 14 (4A) can share 4 electrons
Group 15 (5A) can share 3 electrons
Group 16 (6A) - 2 electrons
Group 17 (7A) - halogens share 1 electron, but they generally form ionic compounds.
Group 18 (8) has filled shells so basically do not form compounds except with F in the case of Kr and Xe.