Which of the following is closest to the atomic mass of sodium (Na)?

• A. 28.09 u
• B. 22.99 u
• C. 12.01 u
• D. 35.45 u

Answer: (B)

Verified step by step guidance

1. Understand that the atomic mass of an element is the weighted average mass of all its naturally occurring isotopes, measured in atomic mass units (u).
2. Recall that sodium (Na) is an element with atomic number 11, and its most common isotope has a mass number close to 23.
3. Recognize that the atomic mass listed on the periodic table for sodium is approximately 22.99 u, reflecting the average mass of its isotopes.
4. Compare the given options (28.09 u, 22.99 u, 12.01 u, 35.45 u) to the known atomic mass of sodium to identify the closest value.
5. Select 22.99 u as the atomic mass closest to sodium's actual atomic mass.