Which of the following is closest to the atomic mass of the element fluorine?

• A. 20.00 u
• B. 19.00 u
• C. 9.00 u
• D. 18.00 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 fluorine has an atomic number of 9, meaning it has 9 protons, and its most common isotope has 9 neutrons, giving it a mass number close to 19.
3. Recognize that the atomic mass listed on the periodic table for fluorine is approximately 19.00 u, reflecting the average mass of its isotopes.
4. Compare the given options (20.00 u, 19.00 u, 9.00 u, 18.00 u) to the known atomic mass of fluorine, which is closest to 19.00 u.
5. Conclude that the value 19.00 u is the best choice because it matches the known atomic mass of fluorine most accurately.