Question

What name should be used for the ionic compound Cu(NO3)2?

Answer 1

copper(II) nitrate

the formula can be rewritten as Cu1(NO3)2

if you take the subscripts, 1 and 2 and make them the charges of the opposite ions, you have:

Cu^2 (NO3)^1

Since the cation is always written first in ionic compounds, the Cu has a 2+ charge and the anion is written second therefore NO3 has a 1- charge:

Cu^2+ (NO3)^1-

Cu is copper but it is a transition metal which means it can have more than one charge.

copper can have a 1+ or a 2+ charge (generally)

in this case it has a 2+ so you need to indicate this in the name by using a roman numeral after the name:

copper(II)

NO3^1- is a polyatomic anion and has a fixed charge and a name (this can be looked up):

nitrate

put the two names together and don't forget the roman numeral:

copper(II) nitrate

Answer 2

Cu(NO₃)₂ is known as Copper (II) Nitrate.

If you ionize it you name it easier:
Cu²⁺ is copper (II) cation
NO₃⁻ is the nitrate radical (poly-atomic ion)
Hence copper (ii) nitrate