Which of the following determines the identity of an element?

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

Answer: (D)

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, called the atomic number, uniquely identifies an element.
4. Note that while the number of neutrons can vary (isotopes) and the number of electrons can change (ions), these do not change the element's identity.
5. Conclude that the atomic mass and number of neutrons do not determine the element's identity, but the number of protons does.