Answer
(a) Rb$_3$N
(b) K$_2$SO$_3$
(c) Rb$_2$SO$_3$
(d) RbNO$_3$
(e) MgSeO$_3$
Work Step by Step
(a) Rb$_3$N
This compound is a simple binary ionic compound. Rubidium is the cation with a valence of 1+, and it's elemental symbol is "Rb." Nitrogen is the anion with a valence of 3-, and it's elemental symbol is "N." We will need three rubidium atoms for every one nitrogen atom to balance the charges in this compound.
(b) K$_2$SO$_3$
This compound contains an oxoanion. Potassium is the cation with a valence of 1+, and it's elemental symbol is "K." Sulfite is the oxoanion with a valence of 2-, and it's representation is "SO$_3$." We will need two potassium atoms for every one sulfite oxoanion to balance the charges in this compound.
(c) Rb$_2$SO$_3$
This compound is a compound containing an oxoanion. Rubidium is the cation with a valence of 1+, and it's elemental symbol is "Rb." Sulfite is the oxoanion with a valence of 2-, and it's symbol is "SO$_3$." We will need two rubidium atoms for every one sulfate oxoanion to balance the charges in this compound.
(d) RbNO$_3$
This compound is a compound containing an oxoanion. Rubidium is the cation with a valence of 1+, and it's elemental symbol is "Rb." Nitrate is the oxoanion with a valence of 1-, and it's symbol is "NO$_3$." The cation and anion combine in a 1:1 ratio. We will need one rubidium atom for every one nitrate oxoanion to balance the charges in this compound.
(e) MgSeO$_3$
This compound contains an oxoanion. Magnesium is the cation with a valence of 2+, and it's elemental symbol is "Mg." Selenite is the anion with a valence of 2-, and it's symbol is "SeO$_3$." The cation and anion combine in a 1:1 ratio. We will need one magnesium atom for every one selenite oxoanion to balance the charges in this compound.
