How do I write these compounds/why, and what type of compound is it? (ionic or covalent)?

Question

Ok I've done the easy ones- but I'm having trouble with these two- I don't know how to write ternary compounds (i'm sure they're easy too- but I just don't know how to)

RbOH and Li(NO3)2

I know what the elements are- but i just don't know how to write them.

Answer 1

The rubidium ion is +1, the hydroxl -1...so RbOH is correct

The lithium ion is +1, the nitrate -1...so LiNO3 is the correct formula.

Both are ionic cmpnds...neither is 'ternary'.

Answer 2

First, look at what compounds you have, starting with RbOH. We know that OH is a hydroxide ion, and that Rb is Rubidium. Looking at the charges of both side (+1 and -1) we can also deduce that these guys are going to be ionicaly bonded as Rubidium Hydroxide (like pottassium hyrdroxide)

The next compound is similar, being ionically boded (they arent both from the right hand side of the periodic table). Therefore, we have di-lithium nitrate (looking at the charges we had +1 and -1*2, therefore we needed 2 lithiums, hence the di)