How are isotopes of an element different from each other?

• A. They have different numbers of electrons in their outer shell.
• B. They have different chemical symbols.
• C. They have different numbers of neutrons.
• D. They have different numbers of protons.

Answer: (C)

Verified step by step guidance

1. Understand that isotopes are variants of the same chemical element, meaning they have the same number of protons but differ in another subatomic particle.
2. Recall that the number of protons defines the element and its chemical symbol, so isotopes must have the same number of protons.
3. Recognize that electrons can vary in ions, but isotopes specifically differ in the nucleus, not in electron count.
4. Identify that isotopes differ in the number of neutrons, which changes the atomic mass but not the chemical properties significantly.
5. Conclude that the key difference between isotopes of an element is the number of neutrons in their nuclei.