Hybridisation of chromium ions in chromate and dichromate ions is respectively

Options

A. `sp^(2)` and `sp^(2)`
B. `sp^(2)` and `sp^(3)`
C. `sp^(3)` and `sp^(2)`
D. `sp^(3)` and `sp^(3)`

Answer

To determine the hybridization of chromium ions in chromate (CrO4²⁻) and dichromate (Cr2O7²⁻) ions, we can follow these steps:

### Step 1: Analyze the Chromate Ion (CrO4²⁻)
1. **Identify the central atom**: In the chromate ion, the central atom is chromium (Cr).
2. **Count the valence electrons**: Chromium has 6 valence electrons.
3. **Determine the number of bonds**: The chromate ion has a tetrahedral structure with four oxygen atoms bonded to the chromium atom. This includes:
- 4 sigma bonds (one from each Cr-O bond).
4. **Count lone pairs**: There are no lone pairs on the chromium atom in the chromate ion.
5. **Calculate the hybridization index**:
- Hybridization index = Number of sigma bonds + Number of lone pairs = 4 (sigma bonds) + 0 (lone pairs) = 4.
6. **Determine hybridization**: A hybridization index of 4 corresponds to sp³ hybridization.

### Step 2: Analyze the Dichromate Ion (Cr2O7²⁻)
1. **Identify the central atoms**: In the dichromate ion, there are two chromium atoms.
2. **Count the valence electrons**: Each chromium has 6 valence electrons, so for two chromium atoms, we have 12 valence electrons.
3. **Determine the number of bonds**: The dichromate ion has a structure where each chromium is bonded to four oxygen atoms, including:
- 4 sigma bonds for each chromium atom (2 from double bonds and 2 from single bonds).
4. **Count lone pairs**: There are no lone pairs on the chromium atoms in the dichromate ion.
5. **Calculate the hybridization index for each chromium atom**:
- Hybridization index = Number of sigma bonds + Number of lone pairs = 4 (sigma bonds) + 0 (lone pairs) = 4.
6. **Determine hybridization**: Each chromium atom in the dichromate ion also has a hybridization index of 4, which corresponds to sp³ hybridization.

### Conclusion
- The hybridization of chromium in the chromate ion (CrO4²⁻) is sp³.
- The hybridization of chromium in the dichromate ion (Cr2O7²⁻) is also sp³.

Thus, the correct answer is that the hybridization of chromium ions in chromate and dichromate ions is respectively sp³ and sp³.

### Final Answer
The hybridization of chromium ions in chromate and dichromate ions is respectively sp³ and sp³.

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