Atomic Structure Atoms:protons,neutrons,and electrons. The number of protons determines the identity of the element. Some atoms of the same element have a different number of neutrons.These are called isotopes. Example:12C,13C,and 14C. => Chapter 1 3 Chapter 1 3 Atomic Structure • Atoms: protons, neutrons, and electrons. • The number of protons determines the identity of the element. • Some atoms of the same element have a different number of neutrons. These are called isotopes. • Example: 12C, 13C, and 14C. =>