Which of the following elements has the greatest average atomic mass?

• A. Uranium (U)
• B. Lead (Pb)
• C. Mercury (Hg)
• D. Gold (Au)

Answer: (A)

Verified step by step guidance

1. Understand that the average atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes, measured in atomic mass units (amu).
2. Recall that the average atomic mass generally increases with the element's position in the periodic table, especially as you move to heavier elements with more protons and neutrons.
3. Identify the atomic numbers and typical atomic masses of the given elements: Lead (Pb), Mercury (Hg), Gold (Au), and Uranium (U).
4. Compare the approximate average atomic masses of these elements: Lead (~207 amu), Mercury (~201 amu), Gold (~197 amu), and Uranium (~238 amu).
5. Conclude that Uranium has the greatest average atomic mass because it has the highest atomic number and the heaviest isotopes among the options.