Neutrons have a mass that is nearly identical to that of protons, but
neutrons have no electric charge. Although neutrons have little effect
on how an atom interacts with others, they do affect the mass and stability
of the nucleus. Isotopes of the same element have the same number of protons
(and therefore of electrons) but differ in the number of neutrons.
| NSES Content Standard B
Physical Science: Structure of atoms Grades 9-12, page 178 The atom's nucleus is composed of protons and neutrons, which are much more massive than electrons. When an element has atoms that differ in the number of neutrons, these atoms are called different isotopes of the element. |