## Chemistry: The Molecular Science (5th Edition)

Recall, the superscript gives the number of protons plus the number of neutrons, so add the number of protons and the number of neutrons to get this number. The subscript, contrarily, indicates the number of protons present. We use this to find the number of neutrons in the given element: The number of neutrons equals the mass number minus the number of protons. Thus: $n = 115-49=66$