Final answer:
A fluorine atom with a mass number of 19 and an atomic number of 9 has 10 neutrons.
Step-by-step explanation:
The question asks about the number of neutrons in a fluorine atom. To find the number of neutrons, one must subtract the atomic number from the mass number of the atom. The atomic number represents the number of protons, and for fluorine (symbol F), this number is 9. The mass number of the most common isotope of fluorine is 19. Therefore, to calculate the number of neutrons in a fluorine atom, you subtract the atomic number (9) from the mass number (19):
Number of neutrons = Mass number - Atomic number = 19 - 9 = 10
Thus, a fluorine atom typically has 10 neutrons