The value of 'b' is ______.

Steps to Solve

1. Identify Chemical Species with Lone Pairs List the chemical species: H2O, SnCl3, Cl2O, BrF3, XeOF2, XeF2, and XeF4. We need to determine the number of lone pairs of electrons on the central atom for each.

2. Analyze H2O In H2O, the central atom is O (oxygen), which has 6 valence electrons. It forms 2 bonds with H atoms and has 2 lone pairs.
   Therefore, H2O has 2 lone pairs.

3. Analyze SnCl3 In SnCl3, the central atom is Sn (tin) which has 4 valence electrons. It forms 3 bonds with Cl atoms and has 1 lone pair.
   Therefore, SnCl3 has 1 lone pair.

4. Analyze Cl2O In Cl2O, the central atom is Cl (chlorine), which has 7 valence electrons. It forms 2 bonds with O and has 2 lone pairs.
   Therefore, Cl2O has 2 lone pairs.

5. Analyze BrF3 In BrF3, the central atom is Br (bromine), which has 7 valence electrons. It forms 3 bonds with F and has 2 lone pairs.
   Therefore, BrF3 has 2 lone pairs.

6. Analyze XeOF2 In XeOF2, the central atom is Xe (xenon), which has 8 valence electrons. It forms 2 bonds with F and 1 bond with O, having 3 lone pairs.
   Therefore, XeOF2 has 3 lone pairs.

7. Analyze XeF2 In XeF2, the central atom is Xe, which again has 8 valence electrons. It forms 2 bonds with F atoms and has 3 lone pairs.
   Therefore, XeF2 has 3 lone pairs.

8. Analyze XeF4 In XeF4, the central atom is Xe, which has 8 valence electrons. It forms 4 bonds with F atoms and has 2 lone pairs.
   Therefore, XeF4 has 2 lone pairs.

9. Count the Species with Two Lone Pairs From the analysis:

   • H2O: 2 lone pairs
   • SnCl3: 1 lone pair
   • Cl2O: 2 lone pairs
   • BrF3: 2 lone pairs
   • XeOF2: 3 lone pairs
   • XeF2: 3 lone pairs
   • XeF4: 2 lone pairs

   Count the species with 2 lone pairs: H2O, Cl2O, BrF3, and XeF4.

10. Final Count The total number of species with two lone pairs is 4.