How many nonbonding electron pairs are there in each of the following molecules: (a) $\mathrm{N}\left(\mathrm{CH}_{3}\right)_{3},(\mathbf{b}) \mathrm{CO},(\mathbf{c}) \mathrm{BF}_{3},$ (d) \(\mathrm{SO}_{2} ?\)

To do this, we need to know the number of valence electrons for each element and then find the total number of valence electrons in each molecule. - Nitrogen (N) has 5 valence electrons - Carbon (C) has 4 valence electrons - Hydrogen (H) has 1 valence electron - Oxygen (O) has 6 valence electrons - Boron (B) has 3 valence electrons - Fluorine (F) has 7 valence electrons - Sulfur (S) has 6 valence electrons Now, let's find the total number of valence electrons for each given molecule: (a) N(CH3)3 has 1 Nitrogen, 3 Carbons, and 9 Hydrogens Total valence electrons = 5(1) + 4(3) + 1(9) = 5 + 12 + 9 = 26 (b) CO has 1 Carbon and 1 Oxygen Total valence electrons = 4(1) + 6(1) = 4 + 6 = 10 (c) BF3 has 1 Boron and 3 Fluorines Total valence electrons = 3(1) + 7(3) = 3 + 21 = 24 (d) SO2 has 1 Sulfur and 2 Oxygens Total valence electrons = 6(1) + 6(2) = 6 + 12 = 18

Now that we have the total number of valence electrons, we can draw the Lewis structure for each molecule. (a) N(CH3)3: - Draw a central Nitrogen atom surrounded by three CH3 groups. - Each Carbon atom is bonded to three Hydrogen atoms. - Nitrogen forms three single bonds with the Carbon atoms, leaving it with one lone electron pair. (b) CO: - Draw a central Carbon atom bonded to an Oxygen atom. - They form a triple bond with the remaining two electron pairs on Oxygen as lone pairs. (c) BF3: - Draw a central Boron atom surrounded by three Fluorine atoms. - Boron forms single bonds with each Fluorine atom, and each Fluorine atom has three lone pairs. (d) SO2: - Draw a central Sulfur atom bonded to two Oxygen atoms. - Sulfur forms a double bond with one Oxygen atom and a single bond with the other Oxygen atom. The Sulfur also has one lone pair of electrons, and the Oxygen atoms each have two lone pairs.

Count the number of nonbonding electron pairs for each molecule: (a) N(CH3)3: - There is one nonbonding electron pair on the Nitrogen atom, and none on the Carbon or Hydrogen atoms, so there is a total of 1 nonbonding electron pair. (b) CO: - There are two nonbonding electron pairs on the Oxygen atom, and none on the Carbon atom. So, there is a total of 2 nonbonding electron pairs. (c) BF3: - There are no nonbonding electron pairs on the Boron atom, and three nonbonding electron pairs on each Fluorine atom, for a total of 3 x 3 = 9 nonbonding electron pairs. (d) SO2: - There is one nonbonding electron pair on the Sulfur atom, and two nonbonding electron pairs on each Oxygen atom, for a total of 1 + 2(2) = 5 nonbonding electron pairs. In summary, for these molecules, there are: (a) N(CH3)3: 1 nonbonding electron pair (b) CO: 2 nonbonding electron pairs (c) BF3: 9 nonbonding electron pairs (d) SO2: 5 nonbonding electron pairs