Which property of an atom determines the identity of a chemical element?

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

Answer: (A)

Verified step by step guidance

1. Understand that the identity of a chemical element is defined by a fundamental property of its atoms.
2. Recall that atoms consist of protons, neutrons, and electrons, each contributing differently to the atom's characteristics.
3. Recognize that the number of protons in the nucleus, also called the atomic number, uniquely identifies an element and determines its chemical behavior.
4. Note that the number of neutrons can vary within atoms of the same element, leading to different isotopes, but does not change the element's identity.
5. Understand that the number of electrons can change in ions, affecting charge but not the elemental identity, and atomic mass is a combination of protons and neutrons, not a defining property.