Which of the following is the atomic mass of fluorine?

• A. 20.00 u
• B. 18.99 u
• C. 19.00 u
• D. 9.00 u

Answer: (C)

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 only one stable isotope, fluorine-19, which means its atomic mass is very close to 19 u.
3. Review the given options and recognize that 19.00 u is the closest to the known atomic mass of fluorine.
4. Note that values like 20.00 u or 18.99 u are not accurate representations of fluorine's atomic mass, and 9.00 u corresponds to the atomic number, not the atomic mass.
5. Conclude that the correct atomic mass of fluorine is approximately 19.00 u based on its isotopic composition.