Which statement about hybridization in the following is not correct ?

Options

A. Hybridization is the mixing of atomic orbitals prior to their combining into molecular orbitals
B. `sp^2` hydbrid orbitals are formed from two p atomic orbitals and one S atomic orbital
C. `d^2sp^3` hybrid orbitals are directed towards the corners of a regular octahedron
D. `sp^3d` hybridd orbitals are all at `90^@` to one another

Answer

To determine which statement about hybridization is not correct, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Hybridization**:
- Hybridization is the process of mixing atomic orbitals to form new hybrid orbitals that are used to create molecular orbitals. This statement is true.

2. **Analyzing the First Statement**:
- The first option states that "the hybridization is the mixing of atomic orbitals prior to combining into molecular orbitals." This is a true statement as it accurately describes the concept of hybridization.

3. **Analyzing the Second Statement**:
- The second option claims that "sp2 hybrid orbitals are formed from 2p orbitals and 1s orbitals." In sp2 hybridization, one s orbital and two p orbitals are indeed mixed to form three sp2 hybrid orbitals. This statement is also true.

4. **Analyzing the Third Statement**:
- The third option states that "d2sp3 hybrid orbitals are directed towards the corners of a regular octahedron." The d2sp3 hybridization involves two d orbitals, one s orbital, and three p orbitals, resulting in an octahedral geometry where the orbitals are directed towards the corners of an octahedron. This statement is true.

5. **Analyzing the Fourth Statement**:
- The fourth option claims that "sp3 hybrid orbitals are all at 90 degrees to one another." In sp3 hybridization, the four sp3 hybrid orbitals are arranged in a tetrahedral geometry with bond angles of approximately 109.5 degrees. Therefore, they are not all at 90 degrees to one another. This statement is false.

### Conclusion:
The statement that is not correct is option number four: "sp3 hybrid orbitals are all at 90 degrees to one another."