# Question ffdf8

Oct 21, 2017

CuS

#### Explanation:

Sulfide: S-2
Copper II: Cu+2 (Note: Cu I: Cu+1)

Therefore neutral Copper II Sulfide: CuS

Oct 21, 2017

$\text{CuS}$

#### Explanation:

The trick here is to realize that the Roman numeral used to name this ionic compound tells you the oxidation state of the metal.

In this case, you know that in copper(II) sulfide, the copper cation carries a $2 +$ charge, i.e. copper is in its $+ 2$ oxidation state, because of the presence of the $\left(\text{II}\right)$ Roman numeral.

Sulfur is located in group 16 of the Periodic Table, which implies that it forms $2 -$ anions. You can thus say that you're dealing with the copper(II) cation, ${\text{Cu}}^{2 +}$, and the sulfide anion, ${\text{S}}^{2 -}$.

As you know, ionic compounds are electrically neutral. This means that the overall positive charge of the cations must be balanced by the overall negative charge of the anions.

You can thus say that a formula unit of copper(II) sulfide will contain one copper(II) cation, which carries a $2 +$ charge, and one sulfide anion, which carries a $2 -$ charge.

["Cu"]^(2+) + ["S"]^(2-) => "Cu"_2"S"_2 => "CuS"#