Q1. Determine the number of valence electrons in: SNF and SbF 5 2 (Multiple choice) SNF = A.18; B. 32; C. 12; SbF 5 2- =A. 98; B. 42; C. 40; Q2. Determine the AXmEn notation of each in TeCl 5 – and ICl 2 + (Multiple choice) TeCl 5 – = A. AX6; B. AX5; C. AX5E; D. AX5E2; ICl 2 + =A. AX2E2; B. AX2E; C. AX2; D. AX4;
The Correct Answer and Explanation is :
Q1. Determining the number of valence electrons
For SNF:
- S (Sulfur) has 6 valence electrons.
- N (Nitrogen) has 5 valence electrons.
- F (Fluorine) has 7 valence electrons.
The total valence electrons for SNF are:
[
6 + 5 + 7 = 18 \, \text{electrons}.
]
Correct answer: A. 18
For SbF₅²⁻:
- Sb (Antimony) has 5 valence electrons.
- Each of the 5 F atoms contributes 7 valence electrons: ( 5 \times 7 = 35 ).
- The extra 2⁻ charge adds 2 electrons.
The total valence electrons for SbF₅²⁻ are:
[
5 + 35 + 2 = 42 \, \text{electrons}.
]
Correct answer: B. 42
Q2. Determining AXmEn notation
For TeCl₅⁻:
- Te (Tellurium) is the central atom with 6 valence electrons.
- 5 Cl atoms are bonded to Te, each contributing 1 bond.
- The negative charge (-1) adds 1 valence electron.
- Total valence electrons around Te = ( 6 + 5 + 1 = 12 ) electrons (6 electron pairs).
- 5 pairs are bonding (AX₅), and 1 is a lone pair (E₁).
Correct AXmEn notation: C. AX₅E
For ICl₂⁺:
- I (Iodine) is the central atom with 7 valence electrons.
- 2 Cl atoms are bonded to I, each contributing 1 bond.
- The positive charge (+1) removes 1 electron.
- Total valence electrons around I = ( 7 + 2 – 1 = 8 ) electrons (4 electron pairs).
- 2 pairs are bonding (AX₂), and 2 are lone pairs (E₂).
Correct AXmEn notation: A. AX₂E₂
Explanation:
Valence electron counting and AXmEn notation rely on understanding the central atom’s electron distribution. The total number of electrons is calculated by summing the central atom’s valence electrons, contributions from bonded atoms, and charges. AXmEn is then derived by identifying bonding pairs (AXₘ) and lone pairs (Eₙ) on the central atom. Correct identification ensures accurate molecular geometry predictions.