Chapter 2 - Atoms, Molecules, and Ions - Exercises - Page 76: 63

a) Barium : $Ba^{2+}$ $\Longrightarrow$Number of protons = 56 $\Longrightarrow$Number of electrons = 54 b) Zinc : $Zn^{2+}$ $\Longrightarrow$Number of protons = 30 $\Longrightarrow$Number of electrons = 28 c)Nitrogen - $N^{3-}$ $\Longrightarrow$Number of protons = 7 $\Longrightarrow$Number of electrons = 10 d) Rubidium: $Rb^{+}$ $\Longrightarrow$Number of protons = 37 $\Longrightarrow$Number of electrons = 36 e) Cobalt: $Co^{3+}$ $\Longrightarrow$Number of protons = 27 $\Longrightarrow$Number of electrons = 24 f) Tellurium : $Te^{2-}$ $\Longrightarrow$Number of protons = 52 $\Longrightarrow$Number of electrons = 54 g) Bromine : $Br^{-}$ $\Longrightarrow$Number of protons = 35 $\Longrightarrow$Number of electrons = 36

a) Barium - $Ba^{2+}$ Atomic number = Z = 56 Thus number of protons = Z = 56. If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) However, the atom is not neutral. The charge ( 2+) indicates that there are two electrons less than the number of protons. (2 protons more give an atom a (2+) positive charge) Thus number of electrons = 56 - 2 = 54 b) Zinc - $Zn^{2+}$ Atomic number = Z = 30 Thus number of protons = Z = 30. If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) However, the atom is not neutral. The charge ( 2+) indicates that there are two electrons less than the number of protons. (2 protons more give an atom a (2+) positive charge) Thus number of electrons = 30 - 2 = 28 c) Nitrogen - $N^{3-}$ Atomic number = Z = 7 Thus number of protons = Z = 7. If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) However, the atom is not neutral. The charge ( 3-) indicates that there are three electrons more than the number of protons. (3 electrons more give an atom a (3-) negative charge) Thus number of electrons = 7 + 3 = 10 d) Rubidium - $Rb^{+}$ Atomic number = Z = 37 Thus number of protons = Z = 37. If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) However, the atom is not neutral. The charge ( +) indicates that there is one electrons less than the number of protons. (1 proton more give an atom a (+) postive charge) Thus number of electrons = 37 - 1 = 36 e) Cobalt- $Co^{3+}$ Atomic number = Z = 27 Thus number of protons = Z = 27. If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) However, the atom is not neutral. The charge ( 3+) indicates that there are two electrons less than the number of protons. (3 protons more give an atom a (3+) positive charge) Thus number of electrons = 27 - 3 = 24 f) Tellurium - $Te^{2-}$ Atomic number = Z = 52 Thus number of protons = Z = 52. If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) However, the atom is not neutral. The charge ( 2-) indicates that there are two electrons more than the number of protons. (2 electrons more give an atom a (2-) negative charge) Thus number of electrons = 52 + 2 = 54 g) Bromine - $Br^{-}$ Atomic number = Z = 35 Thus number of protons = Z = 35. If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) However, the atom is not neutral. The charge ( 1-) indicates that there is one electrons more than the number of protons. (1 electron more give an atom a (1-) negative charge) Thus number of electrons = 35 + 1 = 36