Hydrogen peroxide is an important compound of hydrogen and oxygen. It shows various types of properties and chemical reactions.
The species that do not contain peroxide ion `(s) is//are`.

Options

A. `PbO_2`
B. `SrO_2`
C. `Na_2O_2`
D. `BaO_2`

Explanation

To determine which of the given species does not contain a peroxide ion, we first need to understand what a peroxide ion is. The peroxide ion is represented as \( O_2^{2-} \), where two oxygen atoms are bonded together, and each oxygen has an oxidation state of -1.

Now, let's analyze each of the given options:

1. **PbO2 (Lead(IV) oxide)**:
- In PbO2, lead (Pb) has an oxidation state of +4.
- Therefore, the two oxygen atoms must collectively have an oxidation state of -4 (since +4 from lead must balance with -4 from oxygen).
- Each oxygen in this case has an oxidation state of -2.
- Thus, PbO2 does not contain a peroxide ion.

2. **SrO2 (Strontium peroxide)**:
- Strontium (Sr) has an oxidation state of +2.
- Therefore, the two oxygen atoms must collectively have an oxidation state of -2.
- This means the formula can be written as \( O_2^{2-} \), indicating that SrO2 contains a peroxide ion.

3. **Na2O2 (Sodium peroxide)**:
- Sodium (Na) has an oxidation state of +1.
- With two sodium atoms, the total positive charge is +2.
- The two oxygen atoms must collectively have an oxidation state of -2, which corresponds to \( O_2^{2-} \).
- Therefore, Na2O2 also contains a peroxide ion.

4. **BaO2 (Barium peroxide)**:
- Barium (Ba) has an oxidation state of +2.
- Similar to SrO2, the two oxygen atoms must collectively have an oxidation state of -2, which corresponds to \( O_2^{2-} \).
- Hence, BaO2 contains a peroxide ion as well.

After analyzing all the options, we find that:

- **PbO2** does not contain a peroxide ion.
- **SrO2**, **Na2O2**, and **BaO2** all contain peroxide ions.

Thus, the species that does not contain a peroxide ion is **PbO2**.

### Summary of the Solution:
- **Answer**: PbO2 does not contain a peroxide ion.