Select the elementary substance.
A: silicon dioxide (SiO2)
B: tin (Sn)
C: phosphine (PH3)
Look at the chemical formula for each substance, and count the number of symbols in the formula. Then, decide if the substance is an elementary substance. The chemical formula for tin contains one symbol: Sn. So, tin is made of one chemical element. Substances that are made of one chemical element are elementary substances. So, tin is an elementary substance. The chemical formula for phosphine contains two symbols: P for phosphorus and H for hydrogen. So, phosphine is made of two chemical elements bonded together. Substances that are made of two or more chemical elements bonded together are compounds. So, phosphine is a compound, not an elementary substance. The chemical formula for silicon dioxide contains two symbols: Si for silicon and O for oxygen. So, silicon dioxide is made of two chemical elements bonded together. Substances that are made of two or more chemical elements bonded together are compounds. So, silicon dioxide is a compound, not an elementary substance.