Which of the following properties uniquely identifies every element?

• A. Atomic mass
• B. Mass number
• C. Number of neutrons
• D. Atomic number

Answer: (D)

Verified step by step guidance

1. Understand that each element is uniquely identified by a specific property related to its atomic structure.
2. Recall that the atomic number represents the number of protons in the nucleus of an atom, and this number is unique for each element.
3. Recognize that atomic mass is the weighted average mass of all isotopes of an element and is not unique to a single element because different elements can have similar atomic masses.
4. Know that mass number is the total number of protons and neutrons in a specific isotope of an element, which can vary among isotopes of the same element and is not unique to the element itself.
5. Understand that the number of neutrons can vary even within atoms of the same element (different isotopes), so it does not uniquely identify an element.