If a fluorine atom has a mass number of 19, how many neutrons does it contain?

• A. 1
• B. 10
• C. 9
• D. 19

Answer: (B)

Verified step by step guidance

1. Identify the mass number (A) of the fluorine atom, which is given as 19. The mass number represents the total number of protons and neutrons in the nucleus.
2. Determine the atomic number (Z) of fluorine, which is the number of protons. For fluorine, the atomic number is 9.
3. Use the relationship between mass number, protons, and neutrons: \(A = Z + N\), where \(N\) is the number of neutrons.
4. Rearrange the formula to solve for the number of neutrons: \(N = A - Z\).
5. Substitute the known values into the equation: \(N = 19 - 9\), which will give the number of neutrons in the fluorine atom.