The correct name for Cu (CN) 2

Cupric cyanide or Copper (II) Cyanide

Explanation:

Cu is the chemical symbol for Copper and CN is a polyatomic ion that represents cyanide.

Now, copper has two oxidation states (+1 and + 2) and CN or cyanide has an oxidation state of - 1.

Here's a trick to this:

Cu (CN) ₂

The subscript 2 indicates that there are 2 atoms of CN. The charges of the atoms must be neutral if they will form a compound. Two CN means that they have a combined charge of - 2. Which oxidation state of Copper would make this neutral then?

Cu⁺²

When you name metals with different oxidation states, you name the element first, then write the oxidation state as a roman numeral, enclosed in parentheses.

So for example, Cu ⁺²

Copper (II)

When you name ionic compounds with polyatomic ions, you just name the polyatomic ion, whether it comes first or not.

CN is cyanide

Copper (II) cyanide

If you will use the Latin names, like with Copper (Cuprum) you will add a particular suffix to the root word of the element's Latin name. THe suffix - ic, is used when the atom bonded is in its higher oxidation state, - ous for the lower one.

So since we used Cu⁺² which is the higher one, we use the suffix - ic.

Thus the answer would be:

Cupric Cyanide.