Chromium(II) oxide.
The first thing to recognize here is that you’re dealing with an since you hae a transition metal chromium ##Cr## bonded to a nonmetal oxygen ##O##.
The second important thing to recognize here is that chromium being a transition metal can have multiple which is another way of saying that it can form multiple cations.
This means that you’re going to have to use a Roman numeral to describe its oxidation state in the name of the compound.
So start with what you know. Oxygen being located in group 16 of forms ##2-## anions aclled oxide anions ##O^(2-)##.
Now are always neutral. This means that the positive charge on the chromium cation must balance out the negative charge on the oxide anion.
Since the formula unit for this compound ##CrO## contains one chromium anion and one oxygen anion you can say that the charge on the chromium cation must be equal to ##2+##.
When the cation is always named first followed by the Roman numeral when needed and the anion.
In this case the Roman numeral that must be used is ##(II)## which means that the name of the compound will be
chromium(II) oxide ##->## ##CrO##