Final answer:
The subscript of rubidium in the formula of rubidium sulfate is 2, as two rubidium ions are needed to balance the charge of one sulfate ion, resulting in the formula Rb2SO4.
Step-by-step explanation:
The subscript of rubidium in the formula of rubidium sulfate is 2. The chemical formula for rubidium sulfate can be determined by looking at the charges of the ions that compose the compound. Rubidium has a charge of +1, and since sulfate (SO4) has a charge of -2, it takes two rubidium ions to balance the charge of one sulfate ion. Thus, the formula for rubidium sulfate is Rb2SO4 where the subscript 2 after the Rb indicates there are two rubidium ions in the compound.
In the compound rubidium sulfate (Rb2SO4), the symbol Rb represents the element rubidium. The subscript 2 indicates that there are two rubidium ions present in one molecule of rubidium sulfate.