Which of the following is closest to the atomic mass of chlorine?

• A. 12.01 u
• B. 35.45 u
• C. 18.99 u
• D. 39.10 u

Answer: (B)

Verified step by step guidance

1. Understand that the atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes, measured in atomic mass units (u).
2. Recall that chlorine has two main isotopes: chlorine-35 and chlorine-37, with atomic masses approximately 35 u and 37 u respectively.
3. Recognize that the atomic mass listed on the periodic table (about 35.45 u) reflects the weighted average based on the relative abundance of these isotopes.
4. Compare the given options to the known average atomic mass of chlorine, which is around 35.45 u, to identify the closest value.
5. Conclude that among the options 12.01 u, 18.99 u, 35.45 u, and 39.10 u, the value 35.45 u is closest to the atomic mass of chlorine.