Which of the following factors directly affect the average atomic mass of an element that exists as a mixture of isotopes?

• A. The physical state (solid, liquid, gas) of the element
• B. The color of the element
• C. The relative abundances of each isotope
• D. The temperature at which the element is stored

Answer: (C)

Verified step by step guidance

1. Understand that the average atomic mass of an element is calculated based on the masses of its isotopes and their relative abundances (the proportion of each isotope present).
2. Recall the formula for average atomic mass: \(\text{Average Atomic Mass} = \sum (\text{fractional abundance of isotope} \times \text{mass of isotope})\).
3. Recognize that physical properties like the physical state (solid, liquid, gas) or color do not affect the atomic masses or their relative abundances, so they do not influence the average atomic mass.
4. Note that temperature can affect physical state but does not change the isotopic composition or their relative abundances, so it does not affect the average atomic mass.
5. Conclude that only the relative abundances of each isotope directly affect the average atomic mass of an element.