Isotopes of an Element are Differentiated by Their ____

Question

Isotopes of an element are differentiated by their ____.  
A) atomic weight
B) number of orbital shells
C) element name
D) mass number
E) electron profile

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons, which gives them different mass numbers. Atomic weight (A) is the average of the atomic masses of all isotopes of an element, but it does not differentiate between specific isotopes. The number of orbital shells (B) varies between different elements, not isotopes of the same element. The element name (C) identifies the specific element, but it does not differentiate between isotopes of the same element. The electron profile (E) reflects the arrangement of electrons in an atom, but isotopes of an element have the same electron profile since they have the same number of electrons.