All Isotopes of an Element Have a Different Number of ____

Question

All isotopes of an element have a different number of ____.  
A) electrons
B) protons
C) neutrons
D) orbital shells
E) atoms

Accepted Answer

Isotopes of an element have the same number of protons (which defines the element), but different numbers of neutrons. This leads to variations in the atomic mass of the element, but not its chemical properties.