Which of the following species contains three bond pairs and two lone pairs around the central atom?
Source: https://www.lazynewton.com/questions/chemistry/chemical-bonding-and-molecular-structure/species-bond-pairs-lone-pairs-central-atom-969955
Quick Answer
Option B
— To determine the number of bond pairs and lone pairs around the central atom, we can use the VSEPR theory.
Step-by-step solution
1AnswerB·
To determine the number of bond pairs and lone pairs around the central atom, we can use the VSEPR theory. We need to calculate the steric number (SN) for each species, which is the sum of bond pairs and lone pairs.
Concept: VSEPR Theory and Steric Number
The steric number (SN) is calculated as: SN = (Number of atoms bonded to the central atom) + (Number of lone pairs on the central atom). The number of lone pairs can be found using the formula: Lone pairs = (Total valence electrons - electrons used in bonding) / 2.
Why (B) ClF\u2083 is correct:
- For ClF\u2083:
- Central atom is Cl.
- Valence electrons of Cl = 7.
- Valence electrons of F = 7.
- Total valence electrons = 7 (Cl) + 3 \u00d7 7 (F) = 28.
- Electrons used in bonding = 3 \u00d7 2 (for 3 Cl-F bonds) = 6.
- Remaining electrons = 28 - 6 = 22.
- Number of lone pairs on Cl = (22 - 3 \u00d7 6) / 2 = (22 - 18) / 2 = 4 / 2 = 2 lone pairs. (Alternatively, 22 electrons are distributed among 3 F atoms and Cl. Each F takes 6 lone pair electrons, so 3*6 = 18. Remaining 22-18 = 4 electrons are on Cl, forming 2 lone pairs).
- Number of bond pairs = 3 (from 3 Cl-F bonds).
- So, ClF\u2083 has 3 bond pairs and 2 lone pairs.
Option Analysis:
- A) : Central atom N. Valence electrons of N = 5. Valence electrons of H = 1. Charge = -1. Total valence electrons = 5 + 2 \u00d7 1 + 1 = 8. Electrons used in bonding = 2 \u00d7 2 = 4. Remaining electrons = 8 - 4 = 4. Number of lone pairs = 4 / 2 = 2. Number of bond pairs = 2. (2 bond pairs, 2 lone pairs).
- C) : Central atom O. Valence electrons of O = 6. Valence electrons of H = 1. Total valence electrons = 6 + 2 \u00d7 1 = 8. Electrons used in bonding = 2 \u00d7 2 = 4. Remaining electrons = 8 - 4 = 4. Number of lone pairs = 4 / 2 = 2. Number of bond pairs = 2. (2 bond pairs, 2 lone pairs).
- D) : Central atom B. Valence electrons of B = 3. Valence electrons of F = 7. Total valence electrons = 3 + 3 \u00d7 7 = 24. Electrons used in bonding = 3 \u00d7 2 = 6. Remaining electrons = 24 - 6 = 18. Number of lone pairs on B = 0 (all 18 electrons are lone pairs on F atoms). Number of bond pairs = 3. (3 bond pairs, 0 lone pairs).
Therefore, ClF\u2083 is the correct option.
Correct Answer: (B)