The atomic mass of an element is equal to the number of:

• A. protons and neutrons in the nucleus
• B. protons in the nucleus
• C. electrons in the atom
• D. neutrons in the nucleus

Answer: (A)

Verified step by step guidance

1. Understand that the atomic mass (also called mass number) of an element represents the total number of heavy particles in the nucleus of an atom.
2. Recall that the nucleus contains protons and neutrons, both of which contribute significantly to the atomic mass because they have nearly equal mass.
3. Recognize that electrons have negligible mass compared to protons and neutrons, so they do not significantly affect the atomic mass.
4. Therefore, the atomic mass is the sum of the number of protons and neutrons in the nucleus.
5. Conclude that the correct description of atomic mass is the number of protons and neutrons in the nucleus.