Chapter 2 - Atoms, Molecules, and Ions: Matter Starts Here - Problems - Page 69: 29

(a) 6 protons, 6 electrons, 8 neutrons (b) 26 protons, 26 electrons, 33 neutrons (c) 38 protons, 38 electrons, 52 neutrons (d) 82 protons, 82 electrons, 128 neutrons

(a) We are given the mass number for this particular isotope of carbon, which has the element symbol C. The atomic number of carbon from the periodic table is 6. The atomic number is also the number of protons. Therefore, we have 6 protons in this isotope of carbon. In a neutral atom, the number of protons and the number of electrons are equal, so we have 6 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, 6, from the mass number of 14, we get 8 neutrons. (b) We are given the mass number for this particular isotope of iron, which has the element symbol Fe. The atomic number of iron from the periodic table is 26. The atomic number is also the number of protons. Therefore, we have 26 protons in this isotope of iron. In a neutral atom, the number of protons and the number of electrons are equal, so we have 26 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, 26, from the mass number of 59, we get 33 neutrons. (c) We are given the mass number for this particular isotope of strontium, which has the element symbol Sr. The atomic number of strontium from the periodic table is 38. The atomic number is also the number of protons. Therefore, we have 38 protons in this isotope of iron. In a neutral atom, the number of protons and the number of electrons are equal, so we have 38 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, 38, from the mass number of 90, we get 52 neutrons. (d) We are given the mass number for this particular isotope of lead, which has the element symbol Pb. The atomic number of lead from the periodic table is 82. The atomic number is also the number of protons. Therefore, we have 82 protons in this isotope of iron. In a neutral atom, the number of protons and the number of electrons are equal, so we have 82 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, 82, from the mass number of 210, we get 128 neutrons.