The identity of an element can be determined on the basis of which of the following?

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

Answer: (B)

Verified step by step guidance

1. Understand that the identity of an element is defined by its atomic number, which is the number of protons in the nucleus of its atoms.
2. Recognize that the number of neutrons can vary within atoms of the same element, leading to different isotopes, but this does not change the element's identity.
3. Note that the number of electrons can change when atoms become ions, but this also does not alter the element itself.
4. Realize that atomic mass is the weighted average of all isotopes of an element and is not unique to a single element's identity.
5. Therefore, conclude that the defining characteristic of an element is the number of protons in its nucleus.