Final answer:
A fluorine atom has 10 neutrons, calculated by subtracting its atomic number (9) from its mass number (19).
Step-by-step explanation:
A normal atom of fluorine has 10 neutrons. Fluorine has an atomic number of 9, meaning there are 9 protons in the nucleus. Since the mass number of fluorine is 19, we calculate the number of neutrons by subtracting the atomic number from the mass number: 19 - 9 = 10.
Each element on the periodic table has a unique atomic number, which represents the number of protons present in its nucleus. For fluorine, this atomic number is 9. The mass number, however, represents the total number of protons plus neutrons in the nucleus. We can find this mass number near the element's symbol on the periodic table, which for fluorine is 19. To determine the number of neutrons, we use the simple formula: number of neutrons = mass number - atomic number. Applying this formula to fluorine gives us 19 (mass number) - 9 (atomic number) = 10 neutrons. These neutrons, along with the nine protons, make up the nucleus of the fluorine atom. The presence of neutrons is essential for the stability of the atom's nucleus, balancing the strong repulsive forces between the positively charged protons.