How do I figure out what the symbols are for the cation and anion that make up each ionic compound?

Question

anonymous · Answer

First formula is $$\left( NH _{4} \right)_{2}O$$

ipwnbunnies · Answer

I'm not too sure what you mean.
The cation in an ionic compound is the metal or a polyatomic ion that is positive.
The anion is usually a nonmetal.

ipwnbunnies · Answer

So, in this case, you'll need to know what NH4 is. NH4 is ammonium, which is a positively charged polyatomic ion, so it will be the cation. The cation is positive charged.

ipwnbunnies · Answer

Oxygen, we know is a nonmetal, so it will be the anion.

anonymous · Answer

So the $$NH ^{+1} is that \right for the cation?$$

ipwnbunnies · Answer

Yes, one NH4 molecule has a charge of +1.
But since there are two molecules of NH4 in this compound, the charge will be +2

ipwnbunnies · Answer

Therefore, the oxygen has a charge of -2, so the compound is stable. We know oxygen has an ion charge of -2 in ionic compound because it is two electrons away from becoming a stable atom, like a noble gas.

anonymous · Answer

So what negative charge is the O?

anonymous · Answer

Wouldn't the 4 by on the O? I thought they changed numbers?

ipwnbunnies · Answer

Nooo, the 4 is on the hydrogen. There are 4 Hydrogen atoms in a molecule of NH4.

anonymous · Answer

Oh so the parenteses means that the number stays with the atom that is is with. Is that right?

ipwnbunnies · Answer

Err, yes. Since NH4 is a polyatomic ion, they want to seperate it from the oxygen. And the '2' subscript on the NH4 still denotes 2 molecules of the entire NH4.