Complete the statement.
Ferrous oxide is ().
A: an elementary substance
B: a compound
You can tell whether ferrous oxide is an elementary substance or a compound by counting the number of atomic symbols in its chemical formula. An atomic symbol consists of either one capital letter or a capital letter followed by one or two lowercase letters.
The chemical formula for ferrous oxide, FeO, contains two atomic symbols: Fe for iron and O for oxygen. So, the formula tells you that ferrous oxide is composed of two chemical elements bonded together.
Since ferrous oxide is composed of multiple chemical elements bonded together, ferrous oxide is a compound.