Final answer:
A fluorine atom with an atomic mass of 19 has 10 neutrons in its nucleus, determined by subtracting the atomic number (9) from the atomic mass (19).
Step-by-step explanation:
The question asks how many neutrons are in the nucleus of fluorine with an atomic mass of 19. To find the number of neutrons, we subtract the atomic number, which represents the number of protons, from the atomic mass. Since fluorine has an atomic number of 9 and an atomic mass of 19, we use the following calculation:
Number of neutrons = atomic mass - atomic number
Number of neutrons = 19 - 9
Number of neutrons = 10
Therefore, a normal atom of fluorine with an atomic mass of 19 has 10 neutrons in its nucleus.