Two atoms that are isotopes of one another must have the same number of which subatomic particle?

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

Answer: (A)

Verified step by step guidance

1. Recall that isotopes are atoms of the same element that differ in the number of neutrons but have the same number of protons.
2. Understand that the number of protons defines the element and is called the atomic number.
3. Recognize that electrons can vary in ions, so they are not the defining factor for isotopes.
4. Note that nucleons refer to the total number of protons and neutrons combined, which changes between isotopes.
5. Therefore, isotopes must have the same number of protons but can have different numbers of neutrons.