How is the atomic number of an atom determined?

• A. By subtracting the number of electrons from the number of neutrons
• B. By counting the number of neutrons in the nucleus
• C. By adding the number of protons and electrons
• D. By counting the number of protons in the nucleus

Answer: (D)

Verified step by step guidance

1. Understand that the atomic number of an atom is a fundamental property that defines the element.
2. Recall that the atomic number is equal to the number of protons in the nucleus of the atom.
3. Note that electrons and neutrons do not determine the atomic number; electrons are equal in number to protons in a neutral atom, and neutrons contribute to the atomic mass but not the atomic number.
4. Recognize that subtracting electrons from neutrons or adding protons and electrons does not give the atomic number.
5. Therefore, the atomic number is determined solely by counting the number of protons in the nucleus.