Isotopes of an element differ from one another in the number of which subatomic particles they contain?

• A. Neutrons
• B. Protons
• C. Electrons
• D. Quarks

Answer: (A)

Verified step by step guidance

1. Recall that isotopes are atoms of the same element, meaning they have the same number of protons.
2. Understand that the number of protons defines the element and does not change between isotopes.
3. Recognize that electrons can vary in ions but do not define isotopes.
4. Know that quarks are subatomic particles inside protons and neutrons and are not used to distinguish isotopes.
5. Conclude that isotopes differ in the number of neutrons, which changes the atomic mass but not the element identity.