Final answer:
The element with 19 protons is Potassium (K), so the answer is B) Potassium. Whereas, Fluorine (F) has 9 protons and, thus, 10 neutrons in its most common isotope with a mass number of 19.
Step-by-step explanation:
The element with 19 protons is Potassium (K). This means the correct answer is B) Potassium (K). Now, addressing the separate question about the atomic structure of fluorine, which has an atomic number of 9: a normal atom of fluorine has a mass number of 19. Given that the mass number is the sum of protons and neutrons in the nucleus, and knowing that the number of protons in fluorine is 9, we subtract the atomic number from the mass number to find the number of neutrons, which is 19 - 9 = 10 neutrons.
Fluorine, with its 9 protons, 10 neutrons, and 9 electrons, has a valence shell that contains 7 electrons. To become a fluoride ion (F⁻), fluorine will gain one electron, resulting in a total of 10 electrons. This makes the fluoride ion an anion.