Complete the statement.
Iodine is ().
A: a compound
B: an elementary substance
You can tell whether iodine 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 iodine, I2, contains one atomic symbol: I. So, the formula tells you that iodine is composed of only one chemical element.
Since iodine is composed of only one chemical element, iodine is an elementary substance.