What is the average atomic mass of fluorine?

• A. 18.998 u
• B. 20.998 u
• C. 19.998 u
• D. 17.998 u

Answer: (A)

Verified step by step guidance

1. Identify the isotopes of fluorine and their respective natural abundances. Fluorine has one stable isotope, \(^{19}\mathrm{F}\), with an abundance of nearly 100%.
2. Recall that the average atomic mass is calculated by summing the products of each isotope's mass and its fractional abundance: \( \text{Average Atomic Mass} = \sum (\text{isotope mass} \times \text{fractional abundance}) \).
3. Since fluorine has essentially one isotope, the average atomic mass is approximately equal to the mass of \(^{19}\mathrm{F}\), which is about 18.998 u.
4. Confirm that the given options correspond to possible average atomic masses and select the one closest to the isotope mass weighted by abundance.
5. Conclude that the average atomic mass of fluorine is approximately 18.998 u, reflecting the dominance of the single isotope \(^{19}\mathrm{F}\).