Which of the following best describes what the atomic number of an element represents?

• A. The number of protons in the nucleus of an atom
• B. The total number of neutrons and protons in the atom
• C. The number of electrons in the outermost shell
• D. The mass of the atom in atomic mass units

Answer: (A)

Verified step by step guidance

1. Understand that the atomic number is a fundamental property of an element that uniquely identifies it.
2. Recall that the atomic number corresponds to the number of protons found in the nucleus of an atom of that element.
3. Recognize that the total number of neutrons and protons is called the mass number, not the atomic number.
4. Note that the number of electrons in the outermost shell is related to chemical behavior but does not define the atomic number.
5. Remember that the mass of the atom in atomic mass units is related to the mass number and isotopes, not the atomic number.