13 3.3 Covalent Bonds and Polarity

Figures

Figure 3.3.2: Electronegativity of Elements

A diagram of the s and p blocks on the periodic table displaying the electronegativity values of the elements. The diagram has two large arrows indicating increasing electronegativity across the periodic table-the first arrow begins at the top left and goes to the right; and the second arrow starts from the bottom left and goes vertical to the top of the table. The electronegativity values decrease from flourine in group 7A which has the highest electronegativity at 3.98; moves down to francium in group 1 with the lowest at 0.7. Noble gases do not have an electronegativity value.

Practice questions

Multiple-choice questions

1. Determine the molecular formulas of the H_xS by completing subscripts x=?
   1. 2
   2. 4
   3. 6
   4. 8
2. Determine the molecular formulas of the CCl_z by completing subscripts z=?
   1. 4
   2. 2
   3. 1
   4. 6
3. Determine the molecular formulas of the PF_w by completing subscripts w =?
   1. 1
   2. 2
   3. 3
   4. 4
4. Determine whether the following bonds are ionic, polar covalent, or covalent: between S and Cl.
   1. ionic
   2. polar covalent
   3. covalent
5. Determine whether the following bonds are ionic, polar covalent, or covalent: between N and H.
   1. ionic
   2. polar covalent
   3. covalent
6. Determine whether the following bonds are ionic, polar covalent, or covalent: between C and Br.
   1. ionic
   2. polar covalent
   3. covalent
7. Determine whether the following bonds are ionic, polar covalent, or covalent: between Li and F.
   1. ionic
   2. polar covalent
   3. covalent
8. Carbon, oxygen, nitrogen, halides, and hydrogen are frequently found in molecular compounds. They generally maintain a consistent bonding pattern to acquire an octet in the valence shell. Which of the following statements is not correct regarding the general bonding pattern of the atoms mentioned above?
   1. Carbon forms four covalent bonds
   2. Nitrogen forms three covalent bonds and has one lone pair of electrons
   3. Oxygen forms two covalent bonds and has two lone pairs of electrons
   4. Hydrogen forms one covalent bond and has one lone pair of electrons
9. Which of the following pairs of compounds only contain covalent bonds?
   1. CO, NaCl
   2. NCl₃, CH₄
   3. CH₄, CaCl₂
   4. NaF, FeCl₃
10. The covalent bond that forms between boron and nitrogen is polar covalent. Which of the following options correctly shows the dipoles in the bond?
    1. Bδ+ − Nδ−
    2. Bδ− − Nδ+
    3. Bδ+ − Nδ+
    4. Bδ− − Nδ−
11. Choose the correct Lewis structure for the Cl2 compound.
    1. The chlorine gas Lewis structure consists of two chlorine atoms linked by a triple bond with two lone pairs on each chlorine.
    2. The chlorine gas Lewis structure consists of two chlorine atoms linked by a single bond with three lone pairs on each chlorine.
    3. The chlorine gas Lewis structure consists of two chlorine atoms linked by a single bond with two lone pairs on each chlorine.
12. Choose the correct Lewis structure for the HI compound.
    1. The Lewis structure for hydrogen iodide involves a hydrogen atom single-bonded to an iodine atom with three lone pairs around the iodine atom.
    2. The Lewis structure for hydrogen iodide involves a hydrogen atom single-bonded to an iodine atom with no extra electrons around both iodine and hydrogen atoms.
    3. The resulting Lewis structure for hydrogen iodide involves a hydrogen atom single-bonded to an iodine atom with three lone pairs around both hydrogen and iodine atoms.
13. Choose the correct Lewis structure for the PCl3 compound.
    1. The Lewis structure for phosphorus trichloride involves a central phosphorus atom single-bonded to three chlorine atoms with three lone pairs around each chlorine atom.
    2. The Lewis structure for phosphorus trichloride involves a central phosphorus atom single-bonded to three chlorine atoms with three lone pairs around each chlorine atom and one lone pair around the central phosphorus.
    3. The Lewis structure for phosphorus trichloride involves a central phosphorus atom single-bonded to two chlorine atoms with one lone pair around each chlorine atom and triple-bonded to the third chlorine with one lone pair around it.

Short-answer questions

1. Determine the molecular formulas of HBr_v by completing subscripts v=?
2. Name the following molecular compounds:
   1. BBr₃
   2. CS₂
   3. S₂Cl₂
   4. N₂O₃

Solutions

Multiple-choice questions

1. a
2. a
3. c
4. b
5. b
6. c
7. a
8. d
9. b
10. a
11. b
12. a
13. b

Short-answer questions

1. one/ 1
2. 1. Boron tribromide
   2. Carbon disulfide
   3. Disulphur dichloride
   4. Dinitrogen trioxide