Which of the followingg intermediates contains three paris of electrons in its valence shell?

Options

A. Carbocations
B. Carbanions
C. Free radicals
D. Both (a) and (b)

Answer

To determine which of the given intermediates contains three pairs of electrons in its valence shell, we need to analyze each option carefully. Three pairs of electrons equal six electrons in total. Let's go through the options step by step.

### Step-by-Step Solution:

1. **Understanding the Concept**:
- We need to find an intermediate that has three pairs of electrons, which means it should have a total of six electrons in its valence shell.

2. **Analyzing the First Option: Carbocation**:
- A carbocation has a positive charge on the carbon atom.
- The structure can be represented as follows:
```
H
|
C^+
|
H
```
- In this structure, the carbon is bonded to two hydrogen atoms. Each C-H bond contributes two electrons (one from carbon and one from hydrogen).
- Therefore, the total number of electrons around the carbon in a carbocation is:
- 2 (from one C-H bond) + 2 (from the second C-H bond) + 0 (no lone pairs, as the positive charge indicates a lack of electrons) = 4 electrons.
- Since the positive charge indicates that one electron is missing, we do not count it as part of the valence shell. Thus, a carbocation has **6 electrons** in total, which is equivalent to **three pairs of electrons**.

3. **Analyzing the Second Option: Carbon Ion**:
- A carbon ion has a negative charge on the carbon atom.
- The structure can be represented as follows:
```
H
|
C^-
|
H
```
- In this case, the carbon is still bonded to two hydrogen atoms. However, the negative charge means that there are two additional electrons on the carbon.
- Therefore, the total number of electrons around the carbon in a carbon ion is:
- 2 (from one C-H bond) + 2 (from the second C-H bond) + 2 (from the negative charge) = 6 electrons.
- Thus, a carbon ion has **8 electrons** in total, which is equivalent to **four pairs of electrons**.

4. **Analyzing the Third Option: Free Radical**:
- A free radical has one unpaired electron.
- The structure can be represented as follows:
```
H
|
C•
|
H
```
- In this structure, the carbon is bonded to two hydrogen atoms, and there is one unpaired electron.
- Therefore, the total number of electrons around the carbon in a free radical is:
- 2 (from one C-H bond) + 2 (from the second C-H bond) + 1 (the unpaired electron) = 5 electrons.
- Thus, a free radical has **7 electrons** in total, which is equivalent to **three and a half pairs of electrons**.

5. **Conclusion**:
- Among the three intermediates analyzed, only the **carbocation** has exactly **six electrons**, which corresponds to **three pairs of electrons** in its valence shell.

### Final Answer:
The intermediate that contains three pairs of electrons in its valence shell is **Carbocation**.