Boron occurs naturally as two isotopes. What is the primary difference between these isotopes?

• A. They have different numbers of protons.
• B. They have different numbers of electrons.
• C. They have different chemical properties.
• D. They have different numbers of neutrons.

Answer: (D)

Verified step by step guidance

1. Understand that isotopes are atoms of the same element that have the same number of protons but differ in the number of neutrons.
2. Recall that the number of protons defines the element and its atomic number, so isotopes must have the same number of protons.
3. Recognize that electrons can vary in ions, but isotopes specifically differ in their neutron count, not electrons.
4. Note that chemical properties are mostly determined by the number of protons and electrons, so isotopes generally have very similar chemical behavior.
5. Conclude that the primary difference between isotopes of boron is the number of neutrons in their nuclei.