Chapter 2 - Atoms, Molecules, and Ions: Matter Starts Here - Problems - Page 69: 30

(a) 5 protons, 5 electrons, 6 neutrons (b) 9 protons, 9 electrons, 10 neutrons (c) 53 protons, 53 electrons, 78 neutrons (d) 86 protons, 86 electrons, 136 neutrons

(a) We are given the mass number for this particular isotope of boron, which has the element symbol B. The atomic number of boron from the periodic table is 5. The atomic number is also the number of protons. Therefore, we have 5 protons in this isotope of boron. In a neutral atom, the number of protons and the number of electrons are equal, so we have 5 electrons as well. The mass number is the number of protons added to the number of neutrons, so if we subtract the number of protons, 5, from the mass number of 11, we get 6 neutrons. (b) We are given the mass number for this particular isotope of fluorine, which has the element symbol F. The atomic number of fluorine from the periodic table is 9. The atomic number is also the number of protons. Therefore, we have 9 protons in this isotope of fluorine. In a neutral atom, the number of protons and the number of electrons are equal, so we have 9 electrons as well. The mass number is the number of protons added to the number of neutrons, so if we subtract the number of protons, 9, from the mass number of 19, we get 10 neutrons. (c) We are given the mass number for this particular isotope of iodine, which has the element symbol I. The atomic number of iodine from the periodic table is 53. The atomic number is also the number of protons. Therefore, we have 53 protons in this isotope of iron. In a neutral atom, the number of protons and the number of electrons are equal, so we have 53 electrons as well. The mass number is the number of protons added to the number of neutrons, so if we subtract the number of protons, 53, from the mass number of 131, we get 78 neutrons. (d) We are given the mass number for this particular isotope of radon, which has the element symbol Rn. The atomic number of radon from the periodic table is 86. The atomic number is also the number of protons. Therefore, we have 86 protons in this isotope of radon. In a neutral atom, the number of protons and the number of electrons are equal, so we have 86 electrons as well. The mass number is the number of protons added to the number of neutrons, so if we subtract the number of protons, 86, from the mass number of 210, we get 136 neutrons.