Which of the following determines the identity of an atom?

• A. The total mass of the atom
• B. The number of protons in the nucleus
• C. The number of electrons in the atom
• D. The number of neutrons in the nucleus

Answer: (B)

Verified step by step guidance

1. Understand that the identity of an atom is defined by its atomic number, which is the number of protons in the nucleus.
2. Recall that the atomic number uniquely identifies an element because each element has a different number of protons.
3. Recognize that the total mass of the atom depends on both protons and neutrons, but does not determine the element's identity.
4. Note that the number of electrons can vary in ions and does not change the element itself.
5. Understand that the number of neutrons can vary in isotopes of the same element, so it also does not determine the identity of the atom.