## Chemistry: Principles and Practice (3rd Edition)

(a) $^{9}_{4}$Be$^{2+}$ (b) $^{72}_{32}$Ge$^{2+}$ (c) $^{79}_{35}$Br$^{-}$
(a) The element with 4 protons in the nucleus, which means the atomic number is 4, is beryllium, chemical symbol Be. The superscript to the left of the chemical symbol would be the mass number, which is the total number of protons and neutrons in the nucleus of that atom. We add the number of protons, 4, to the number of neutrons, 5, to get a mass number of 9. The left subscript is the atomic number, which is 4. The superscript to the right of the chemical symbol is the charge of the ion. We figure this out by adding up the negative and positive charges to get a net charge. There are 4 protons, each with a single positive charge for a total charge of +4. The number of electrons is 2, each with a single negative charge for a total charge of -2. We add +4 to -2 to get a net charge of +2. The symbol for this ion would be $^{9}_{4}$Be$^{2+}$. (b) The element with 32 protons in the nucleus, which means the atomic number is 32, is germanium, chemical symbol Ge. The superscript to the left of the chemical symbol would be the mass number, which is the total number of protons and neutrons in the nucleus of that atom. We add the number of protons, 32, to the number of neutrons, 40, to get a mass number of 72. The left subscript is the atomic number, which is 32. The superscript to the right of the chemical symbol is the charge of the ion. We figure this out by adding up the negative and positive charges to get a net charge. There are 32 protons, each with a single positive charge for a total charge of +32. The number of electrons is 30, each with a single negative charge for a total charge of -30. We add +32 to -30 to get a net charge of +2. The symbol for this ion would be $^{72}_{32}$Ge$^{2+}$. (c) The element with 35 protons in the nucleus, which means the atomic number is 35, is bromine, chemical symbol Br. The superscript to the left of the chemical symbol would be the mass number, which is the total number of protons and neutrons in the nucleus of that atom. We add the number of protons, 35, to the number of neutrons, 44, to get a mass number of 79. The left subscript is the atomic number, which is 35. The superscript to the right of the chemical symbol is the charge of the ion. We figure this out by adding up the negative and positive charges to get a net charge. There are 35 protons, each with a single positive charge for a total charge of +35. The number of electrons is 36, each with a single negative charge for a total charge of -36. We add +35 to -36 to get a net charge of -1. The symbol for this ion would be $^{79}_{35}$Br$^{-}$.