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
