Question

What is the number of bond pair of electrons and lone pair of electrons present in the valence shell of chalcogens in their hydride ?

• A. 2 - Bond pair and 1- lone pair of electrons
• B. 2 - Bond pair and 2- lone pair of electrons
• C. 3 - Bond pair and 1- lone pair of electrons
• D. 3 - Bond pair and 2- lone pair of electrons

Hint:

Chalcogens have 6 valence electrons and form H2X, so two electrons are shared and two pairs stay unshared.

Answer 1

The Correct Option is B

Step 1: Understand the question
Chalcogens are the group 16 elements (O, S, Se, Te). Each has 6 electrons in its valence shell. Their hydrides have the general formula \(\text{H}_2\text{X}\), such as \(\text{H}_2\text{O}\) and \(\text{H}_2\text{S}\).

Step 2: Count bond pairs
Each hydrogen shares one electron with the central atom through one single bond. Two hydrogens give 2 bond pairs.

Step 3: Count lone pairs
Of the 6 valence electrons, 2 are used in bonding. The remaining 4 electrons form \(4/2 = 2\) lone pairs.

Step 4: Conclusion with check
Total electron pairs around X is 4 (2 bond + 2 lone), which gives a bent shape, as seen in water. Options with 3 bond pairs would need three hydrogens (like \(\text{NH}_3\)), and an option with only 1 lone pair would leave the valence shell short of the 6 electrons that group 16 has.

Final Answer:
The hydride has 2 bond pairs and 2 lone pairs. This is option (B). \[ \boxed{\text{(B) }2 \text{ bond pairs and } 2 \text{ lone pairs}} \]