Complete the statement.
Boron nitride is ().

 - an elementary substance
 - a compound
You can tell whether boron nitride 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 boron nitride, BN, contains two atomic symbols: B for boron and N for nitrogen. So, the formula tells you that boron nitride is composed of two chemical elements bonded together.
Since boron nitride is composed of multiple chemical elements bonded together, boron nitride is a compound.