Which of the following best describes an isotope?

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

Answer: (A)

Verified step by step guidance

1. Recall that isotopes are variants of the same chemical element, meaning they have the same number of protons but differ in the number of neutrons.
2. Understand that the number of protons defines the element, so isotopes must have the same proton count to be considered the same element.
3. Recognize that the difference in neutrons affects the atomic mass but not the chemical properties significantly.
4. Eliminate options that describe atoms with different elements (different proton numbers) or differences in electrons, as these do not define isotopes.
5. Conclude that the best description of an isotope is 'Atoms of the same element with different numbers of neutrons.'