Drago suggested an emprical rule which is compatible with the energetics of hybridization. It will occupy a stereochemically inactive s-orbital, and the bonding will be through p-orbitals and bond angles will be nearly `90^(@)` if the electronegativity of the surrounding atoms is `le2.5`.
Q. In which of the following molecule central atom has higher % s-character in its bond pair:

Options

A. `AsH_(3)`
B. `GeH_(4)`
C. `P_(4)`
D. `H_(2)Se`

Answer

To determine which molecule has a central atom with the highest percentage of s-character in its bond pairs according to Drago's empirical rule, we will analyze the given options step by step.

### Step 1: Understand Drago's Rule
Drago's rule states that:
1. The central atom should have at least one lone pair of electrons.
2. The central atom should belong to group 13 to 16 or from the 3rd to 7th period.
3. The electronegativity of the surrounding atoms should be less than or equal to 2.5.
4. If there are four lone pairs, sigma bonds are absent.

### Step 2: Analyze Each Molecule
We will analyze the central atom of each molecule provided in the options to determine the percentage of s-character.

1. **Arsenic (As) in Arsenic Compounds (e.g., AsH3)**:
- Group: 15 (has 5 valence electrons)
- Lone pairs: 1 (3 used for bonding)
- Hybridization: None needed according to Drago's rule.
- s-character: 33.33% (since it can be considered as having sp3 hybridization if needed).

2. **Germanium (Ge) in GeH4**:
- Group: 14 (has 4 valence electrons)
- Lone pairs: 0 (all electrons are used for bonding)
- Hybridization: sp3 (due to 4 bonds).
- s-character: 25%.

3. **Phosphorus (P) in P4**:
- Group: 15 (has 5 valence electrons)
- Lone pairs: 1 (3 used for bonding with other P atoms)
- Hybridization: None needed according to Drago's rule.
- s-character: 33.33%.

4. **Selenium (Se) in H2Se**:
- Group: 16 (has 6 valence electrons)
- Lone pairs: 2 (2 used for bonding with H)
- Hybridization: None needed according to Drago's rule.
- s-character: 50% (considering it as having sp2 hybridization).

### Step 3: Compare s-Character
Now we compare the percentage of s-character in the bond pairs of the central atoms:
- As: 33.33%
- Ge: 25%
- P: 33.33%
- Se: 50%

### Conclusion
The molecule with the central atom that has the highest percentage of s-character is **H2Se**, where selenium has 50% s-character in its bond pairs.

### Final Answer
**H2Se** has the highest percentage of s-character in its bond pair.

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