True order of bond angle among group -16 hydrides is

Options

A. `H_(2)O gt H_(2)S gt H_(2)Se gt H_(2) Te`
B. `H_(2) Te gt H_(2) Se gt H_(2) S gt H_(2)O`
C. `H_(2)S gt H_(2)O gt H_(2) Se gt H_(2) Te`
D. `H_(2) O gt H_(2)S gt H_(2) Te gt H_(2) Se`

Answer

To determine the true order of bond angles among group 16 hydrides (H2O, H2S, H2Se, H2Te), we need to analyze the factors affecting bond angles in these molecules.

### Step-by-Step Solution:

1. **Identify the Group 16 Hydrides**:
The group 16 hydrides we are considering are:
- H2O (water)
- H2S (hydrogen sulfide)
- H2Se (hydrogen selenide)
- H2Te (hydrogen telluride)

2. **Understand the Trend in Atomic Size**:
As we move down the group from oxygen to tellurium, the size of the central atom increases. This is due to the addition of electron shells as we go from H2O to H2Te.

3. **Consider Electronegativity**:
Electronegativity decreases as we move down the group. Oxygen is the most electronegative, while tellurium is the least. This affects the ability of the central atom to attract the bonding electrons.

4. **Analyze Bond Pair-Bond Pair Repulsions**:
The bond pair-bond pair repulsions are stronger in smaller atoms (like oxygen) compared to larger atoms (like tellurium). As the size of the central atom increases, the repulsions between the bond pairs decrease.

5. **Determine the Effect on Bond Angles**:
Due to the decrease in bond pair-bond pair repulsions as we move down the group, the bond angles also decrease. This means that the bond angles will be largest in H2O and smallest in H2Te.

6. **List the Bond Angles**:
- H2O: approximately 104.5 degrees
- H2S: approximately 92.2 degrees
- H2Se: approximately 91 degrees
- H2Te: approximately 90 degrees

7. **Conclude the Order of Bond Angles**:
The order of bond angles from largest to smallest is:
H2O > H2S > H2Se > H2Te

### Final Answer:
The true order of bond angles among group 16 hydrides is:
**H2O > H2S > H2Se > H2Te**