Answer
(a) $Rb_3N$
(b) $K_2Se$
(c) $Rb_2SO_3$
(d) $RbNO_3$
(e) $MgSO_3$
Work Step by Step
(a) Rubidium (Rb) has an oxidation number of $1+$. Nitrogen (N) has an oxidation number of $3-$. Rubidium and nitrogen combine in a three-to-one ratio. Therefore, the formula for rubidium nitride is $Rb_3N$.
(b) Potassium (K) has an oxidation number of $1+$. Selenium (Se) has an oxidation number of $2-$. Potassium and selenium combine in a two-to-one ratio. Therefore, the formula for potassium selenide is $K_2Se$.
(c) Rubidium (Rb) has an oxidation number of $1+$. Sulfite ($SO_3^{2-}$) has an oxidation number of $2-$. Rubidium and sulfite combine in a two-to-one ratio. Therefore, the formula for rubidium sulfite is $Rb_2SO_3$.
(d) Rubidium (Rb) has an oxidation number of $1+$. Nitrate ($NO_3^{-}$) has an oxidation number of $1-$. Rubidium and nitrate combine in a one-to-one ratio. Therefore, the formula for rubidium nitrate is $RbNO_3$.
(e) Magnesium (Mg) has an oxidation number of $2+$. Sulfite ($SO_3^{2-}$) has an oxidation number of $2-$. Magnesium and sulfite combine in a one-to-one ratio. Therefore, the formula for magnesium sulfite is $MgSO_3$.
