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

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