Which of the following factors directly affects 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.
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 state, color, and storage temperature do not change the isotopic composition or their relative abundances.
4. Identify that only the relative abundances of each isotope directly affect the average atomic mass because they determine how much each isotope contributes to the overall mass.
5. Conclude that changes in isotopic abundances will change the weighted average, thus affecting the average atomic mass.