Question

From the given covalent compounds (A to F) identify the pair of molecules which have:
(i) Two lone pairs of electrons on the central atom.
(ii) One lone pair of electrons on the central atom.
A. \(SO_2\)
B. \(ClF_3\)
C. \(BF_3\)
D. \(BrF_5\)
E. \(XeF_4\)
F. \(SF_6\)

• A. (i) A & F (ii) A & E
• B. (i) D & F (ii) C & D
• C. (i) B & E (ii) A & D
• D. (i) C & A (ii) B & C

Hint:

Use VSEPR: Lone pairs = (valence electrons - bonding electrons)/2. Quickly identify shapes and lone pairs together.

Answer 1

The Correct Option is C

Step 1: Determine lone pairs using VSEPR theory.
Count total valence electrons and bonding pairs to find lone pairs on central atom.

Step 2: Analyse \(ClF_3\) (B).
Central atom Cl has 7 valence electrons.
It forms 3 bonds with F atoms, leaving 2 lone pairs.
\[ ClF_3 \Rightarrow 2 \text{ lone pairs} \]

Step 3: Analyse \(XeF_4\) (E).
Xe has 8 valence electrons.
It forms 4 bonds, leaving 2 lone pairs.
\[ XeF_4 \Rightarrow 2 \text{ lone pairs} \]
Thus, (i) includes B and E.

Step 4: Analyse \(SO_2\) (A).
S has 6 valence electrons.
After bonding, one lone pair remains.
\[ SO_2 \Rightarrow 1 \text{ lone pair} \]

Step 5: Analyse \(BrF_5\) (D).
Br has 7 valence electrons.
Forms 5 bonds, leaving 1 lone pair.
\[ BrF_5 \Rightarrow 1 \text{ lone pair} \]
Thus, (ii) includes A and D.

Step 6: Check remaining molecules.
\[ BF_3 \Rightarrow 0 \text{ lone pairs} \]
\[ SF_6 \Rightarrow 0 \text{ lone pairs} \]

Step 7: Final conclusion.
\[ \boxed{(i)\ B,E \quad (ii)\ A,D} \]