Isotopes of an element will always differ in:

• A. chemical properties
• B. number of electrons
• C. number of protons
• D. number of neutrons

Answer: (D)

Verified step by step guidance

1. Understand that isotopes are atoms of the same element that have the same number of protons but differ in the number of neutrons.
2. Recall that the number of protons defines the element and its chemical properties, so isotopes have identical chemical properties because they have the same number of protons and electrons.
3. Recognize that the number of electrons in a neutral atom equals the number of protons, so isotopes of the same element have the same number of electrons.
4. Note that the difference in isotopes lies in the number of neutrons, which affects the atomic mass but not the chemical behavior.
5. Therefore, isotopes of an element always differ in the number of neutrons.