In what way do isotopes of an element differ from each other?

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

Answer: (D)

Verified step by step guidance

1. Recall that isotopes are atoms of the same element, meaning they have the same number of protons, which defines the element's identity.
2. Understand that the chemical symbol of an element is determined by its number of protons, so isotopes share the same chemical symbol.
3. Recognize that the number of electrons in the outer shell can vary in ions, but isotopes specifically differ in their nuclear composition, not electron configuration.
4. Focus on the nucleus: isotopes differ in the number of neutrons they contain, which changes their mass but not their chemical properties significantly.
5. Therefore, the key difference between isotopes of an element is that they have different numbers of neutrons.