In formation of ethene, the bond formation between s and p- orbitals takes place in the following manner.

Options

A. `sp^(2)` hybridised orbitals form sigma bond while the unhybridised `(p_(x) or p_(y))` overlaps sidewise to form `pi `- bond.
B. `sp^(2)` hybridised orbitals form `pi`- bond while the unhybridised `(p_(z))` overlaps to form `sigma`-bond.
C. `sp^(2)` hybridised orbitals overlap with s- orbitals of H atoms while unhybridised orbitals form C - C bond.
D. `sp^(2)` hybridised orbitals form sigma bonds with H atoms while unhybridised orbitals form `sigma` bonds between C atoms.

Explanation

To understand the bond formation in ethene (C2H4), we need to analyze the hybridization of the carbon atoms and how the bonds are formed between the carbon and hydrogen atoms.

### Step-by-Step Solution:

1. **Identify the Structure of Ethene**:
- Ethene consists of two carbon atoms (C) and four hydrogen atoms (H). The molecular structure can be represented as H2C=CH2, indicating a double bond between the two carbon atoms.

2. **Determine the Hybridization of Carbon**:
- Each carbon atom in ethene is bonded to three other atoms (two hydrogen atoms and one carbon atom). To accommodate these bonds, carbon undergoes hybridization.
- In ethene, each carbon atom is **sp² hybridized**. This means that one s orbital and two p orbitals from each carbon atom combine to form three equivalent sp² hybrid orbitals.

3. **Formation of Sigma Bonds**:
- The sp² hybridized orbitals from each carbon atom overlap with the s orbitals of hydrogen atoms to form **sigma (σ) bonds**.
- Specifically, each carbon forms two sigma bonds with two hydrogen atoms and one sigma bond with the other carbon atom.

4. **Formation of Pi Bonds**:
- The remaining unhybridized p orbital on each carbon atom (the third p orbital) is used to form a **pi (π) bond**.
- This occurs through the **sidewise overlap** of the unhybridized p orbitals from each carbon atom.

5. **Conclusion**:
- In ethene, the bonding can be summarized as follows:
- **Sigma bonds** are formed by the overlap of sp² hybridized orbitals (C-H and C-C).
- **Pi bond** is formed by the sidewise overlap of the unhybridized p orbitals.

### Final Answer:
The correct statement regarding the bond formation in ethene is:
- **Option A**: sp² hybridized orbitals form sigma bonds while unhybridized orbitals overlap sidewise to form pi bonds.