To determine the oxidation number of rubidium (Rb) in the compounds Rb₂O, Rb₂O₂, and RbO₂, we can follow these steps:
### Step 1: Determine the oxidation number in Rb₂O
1. Let the oxidation number of rubidium be \( x \).
2. In Rb₂O, there are 2 rubidium atoms and 1 oxygen atom.
3. The oxidation number of oxygen is typically \(-2\).
4. The equation can be set up as follows:
\[
2x + (-2) = 0
\]
5. Simplifying gives:
\[
2x - 2 = 0 \implies 2x = 2 \implies x = +1
\]
6. Therefore, the oxidation number of rubidium in Rb₂O is \( +1 \).
### Step 2: Determine the oxidation number in Rb₂O₂
1. Again, let the oxidation number of rubidium be \( x \).
2. In Rb₂O₂, there are 2 rubidium atoms and 2 oxygen atoms.
3. The oxidation number of oxygen remains \(-2\).
4. The equation can be set up as:
\[
2x + 2(-2) = 0
\]
5. Simplifying gives:
\[
2x - 4 = 0 \implies 2x = 4 \implies x = +2
\]
6. However, since rubidium is an alkali metal, its oxidation number cannot exceed \( +1 \). Thus, we conclude that the oxidation number of rubidium in Rb₂O₂ is also \( +1 \).
### Step 3: Determine the oxidation number in RbO₂
1. Let the oxidation number of rubidium be \( x \).
2. In RbO₂, there is 1 rubidium atom and 2 oxygen atoms.
3. The oxidation number of oxygen is \(-2\).
4. The equation can be set up as:
\[
x + 2(-2) = 0
\]
5. Simplifying gives:
\[
x - 4 = 0 \implies x = +4
\]
6. Again, since rubidium is an alkali metal, its oxidation number cannot exceed \( +1 \). Thus, the oxidation number of rubidium in RbO₂ is also \( +1 \).
### Final Conclusion
The oxidation numbers of rubidium in Rb₂O, Rb₂O₂, and RbO₂ are respectively:
- Rb₂O: \( +1 \)
- Rb₂O₂: \( +1 \)
- RbO₂: \( +1 \)
Thus, the answer is \( +1, +1, +1 \).
