Which part of the atom determines the identity of an element?

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

Answer: (A)

Verified step by step guidance

1. Understand that the identity of an element is defined by a unique characteristic of its atoms.
2. Recall that atoms consist of protons, neutrons, and electrons, each with different roles.
3. Recognize that the number of protons in the nucleus is called the atomic number, which uniquely identifies an element.
4. Note that the total mass of the atom depends on both protons and neutrons but does not determine the element's identity.
5. Understand that the number of neutrons can vary in isotopes of the same element, and the number of electrons can change in ions, so neither defines the element itself.