`RbO_2` is

Options

A. peroxide and diamagnetic
B. superoxide and paramagnetic
C. peroxide and paramangetic
D. superoxide and diamagnetic

Explanation

To determine the nature of `RbO2`, we need to analyze its composition and properties step by step.

### Step-by-Step Solution:

1. **Identify the Compound**:
- The chemical formula `RbO2` indicates that it consists of rubidium (Rb) and oxygen (O).

2. **Determine the Oxidation State of Oxygen**:
- In `RbO2`, the oxygen is in the form of a superoxide ion (O2^−). In superoxides, the oxidation state of oxygen is -1/2 for each oxygen atom, but collectively, it can be considered as -1 for the O2^− ion.

3. **Classify the Compound**:
- Based on the oxidation state of oxygen, `RbO2` is classified as a superoxide. Therefore, it is rubidium superoxide.

4. **Check for Paramagnetism or Diamagnetism**:
- To determine if `RbO2` is paramagnetic or diamagnetic, we need to analyze the electronic configuration of the superoxide ion (O2^−).
- The molecular orbital electronic configuration for O2^− is:
- σ1s², σ*1s², σ2s², σ*2s², σ2p_z², π2p_x², π2p_y², π*2p_x², π*2p_y¹
- This configuration shows that there is one unpaired electron in the π*2p_y orbital.

5. **Conclusion**:
- Since there is an unpaired electron in the O2^− ion, `RbO2` is paramagnetic.

### Final Answer:
`RbO2` is a **superoxide** and is **paramagnetic**.

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