Complete the statement.
Bromine is ().

 - a compound
 - an elementary substance
You can tell whether bromine 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 bromine, Br2, contains one atomic symbol: Br. So, the formula tells you that bromine is composed of only one chemical element.
Since bromine is composed of only one chemical element, bromine is an elementary substance.