Which of the following statements best describes an isotope?

• A. Atoms of different elements with the same mass number
• B. Atoms of different elements with the same number of protons
• C. Atoms of the same element with different numbers of electrons
• D. Atoms of the same element with different numbers of neutrons

Answer: (D)

Verified step by step guidance

1. Recall that isotopes are variants of the same element, meaning they have the same number of protons (which defines the element).
2. Understand that the mass number of an atom is the sum of its protons and neutrons, so isotopes differ in the number of neutrons.
3. Recognize that atoms of different elements have different numbers of protons, so they cannot be isotopes of each other.
4. Note that atoms with different numbers of electrons are called ions or charged species, not isotopes.
5. Therefore, the best description of an isotope is: atoms of the same element with different numbers of neutrons.