The number of protons in one atom of an element determines the atom's:

• A. isotopic abundance
• B. atomic number
• C. number of neutrons
• D. mass number

Answer: (B)

Verified step by step guidance

1. Understand that an atom is composed of protons, neutrons, and electrons. The number of protons defines the identity of the element.
2. Recall that the atomic number is defined as the number of protons in the nucleus of an atom.
3. Recognize that isotopic abundance refers to the relative amount of different isotopes of an element, which differ in the number of neutrons, not protons.
4. Know that the mass number is the total number of protons and neutrons in the nucleus, so it depends on both, not just protons.
5. Therefore, the number of protons uniquely determines the atomic number, which identifies the element.