Which term describes the weighted average mass of the isotopes of an element?

• A. Atomic mass
• B. Atomic number
• C. Mass number
• D. Molar mass

Answer: (A)

Verified step by step guidance

1. Understand that elements can have multiple isotopes, which are atoms with the same number of protons but different numbers of neutrons, resulting in different masses.
2. Recognize that the weighted average mass takes into account both the mass and the relative abundance of each isotope of an element.
3. Recall that the term 'Atomic mass' refers to this weighted average mass of all naturally occurring isotopes of an element, expressed in atomic mass units (amu).
4. Differentiate this from 'Atomic number,' which is the number of protons in an atom and does not involve isotopes or mass averaging.
5. Note that 'Mass number' is the total number of protons and neutrons in a single isotope, and 'Molar mass' is the mass of one mole of an element or compound, usually expressed in grams per mole.