Can anyone explain why Cu(ClO4)2 is named copper (II) perchlorate? I know the copper (II) is using the stock system but I'm wondering where the II comes from. And why is the "per" being used before "chlorate" (I know that this means 'additional' oxygen, but where is this additional oxygen in the formula?)
Lets split this up into two parts. We have Copper II (Cu 2+) and a Perchlorate ion (ClO4-). The copper II is named so because metals tend to have a variety of charges and this is how we know the charge on this particular metal. Copper II means it has a charge of +2. Now we look at our perchlorate ion, which is a polyatomic like Nitrate (NO3), Sulfate (SO4), Carbonate (CO3 etc.). All polyatomic ions have a predetermined charge, a perchlorate ion will almost always have a minus 1 charge. Now if you take the two ions together, you need to cross the charges, making them the subscripts. Since Copper II has a +2 charge, you will have 2 perchlorate ions. Since a perchlorate ion has a -1 charge, you will have 1 copper ion. Therefore Cu(ClO4)2
The copper (ll) refers to the Cu being in its +2 valence state, rather than its other possible state of +1, which is designated Cu (l) The PERchlorate differentiates the (ClO4)- ion from the (ClO3)- chlorate ion. 'per' because an added O is present.
