Name each of the following oxides. Assuming that the compounds are ionic, what charge is associated with the metallic element in each case? \((\mathbf{a})\) \(\mathrm{NiO},(\mathbf{b}) \mathrm{MnO}_{2},(\mathbf{c}) \mathrm{Cr}_{2} \mathrm{O}_{3}\) \((\mathbf{d}) \mathrm{MoO}_{3}\)

In all these compounds, oxygen is the non-metal element and has an oxidation state of -2. Now, let's identify the metallic elements in each compound: a) NiO b) MnO₂ c) Cr₂O₃ d) MoO₃

Using the oxidation state rules and knowing that the sum of oxidation states equals the overall charge on the compound, we can determine the oxidation state of the metallic elements. a) NiO Ni - unknown oxidation state O - (-2) oxidation state Ni + (-2) = 0 Ni = +2 The nickel has a charge of +2 in this compound. b) MnO₂ Mn - unknown oxidation state 2 x O - (-2) x 2 = -4 Mn + (-4) = 0 Mn = +4 The manganese has a charge of +4 in this compound. c) Cr₂O₃ 2 x Cr - 2 x unknown oxidation state 3 x O - (-2) x 3 = -6 2 x Cr + (-6) = 0 2 x Cr = +6 Cr = +3 Each chromium atom has a charge of +3 in this compound. d) MoO₃ Mo - unknown oxidation state 3 x O - (-2) x 3 = -6 Mo + (-6) = 0 Mo = +6 The molybdenum has a charge of +6 in this compound.

Now that we have found the charge of the metallic element in each compound, we can name the oxides: a) NiO - Nickel(II) oxide, nickel has a +2 charge b) MnO₂ - Manganese(IV) oxide, manganese has a +4 charge c) Cr₂O₃ - Chromium(III) oxide, each chromium atom has a +3 charge d) MoO₃ - Molybdenum(VI) oxide, molybdenum has a +6 charge