Answer
manganese (IV) oxide
+4
Work Step by Step
$MnO_2$
$Mn$ is manganese.
$O$ is oxygen, which his called oxide when naming compounds.
Oxygen has a charge of -2. The compound is neutral, so the charge/oxidation number of the manganese element was +4 (-2*2 because there are 2 oxygen atoms in the compound).
The name is written as element(oxidation number) element so
$MnO$ is manganese (IV) oxide.
