You can tell whether fluorine 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 fluorine, F2, contains one atomic symbol: F. So, the formula tells you that fluorine is composed of only one chemical element.
Since fluorine is composed of only one chemical element, fluorine is an elementary substance.
Complete the statement.
Fluorine is ().
A: a compound
B: an elementary substance