Question

prepwork: covalent compounds
name:
for each molecule below, draw the lewis dot diagram and name the molecule.

1. cf₄

lewis dot diagram
name:

1. sef₂

name:

1. nh₃

name:

1. ccl₄

name:

1. cs₂

name:

1. h₂o₂

name:

1. chcl₃

name:

1. c₂h₅cl (hint: both carbons should go in the center of your molecule)

name:

Answer:

1. $\boldsymbol{CF_4}$

Lewis Dot Diagram:

• Carbon (C) is central, has 4 valence electrons.
• Four Fluorine (F) atoms, each with 7 valence electrons.
• C forms 4 single bonds with F (sharing 1 electron pair each).
• Each F has 3 lone pairs (6 electrons) after bonding.

(Diagram: C in center, 4 F atoms around it, each F with 3 lone pairs, C - F bonds as electron pairs.)

Naming:

• Prefix for C: “carbon” (1 atom, no prefix).
• Prefix for F: “tetra-” (4 atoms) + “fluorine” → “tetrafluoride”.
• Name: Carbon Tetrafluoride

2. $\boldsymbol{SeF_2}$

Lewis Dot Diagram:

• Selenium (Se) is central, has 6 valence electrons.
• Two Fluorine (F) atoms, each with 7 valence electrons.
• Se forms 2 single bonds with F (sharing 1 electron pair each).
• Se has 2 lone pairs (4 electrons) left.
• Each F has 3 lone pairs (6 electrons) after bonding.

(Diagram: Se in center, 2 F atoms (single bonds), Se with 2 lone pairs, F with 3 lone pairs each.)

Naming:

• Prefix for Se: “selenium” (1 atom, no prefix).
• Prefix for F: “di-” (2 atoms) + “fluorine” → “difluoride”.
• Name: Selenium Difluoride

3. $\boldsymbol{NH_3}$

Lewis Dot Diagram:

• Nitrogen (N) is central, has 5 valence electrons.
• Three Hydrogen (H) atoms, each with 1 valence electron.
• N forms 3 single bonds with H (sharing 1 electron pair each).
• N has 1 lone pair (2 electrons) left.

(Diagram: N in center, 3 H atoms (single bonds), N with 1 lone pair.)

Naming:

• Common name: Ammonia (systematic: Nitrogen Trihydride, but “ammonia” is standard).

4. $\boldsymbol{CCl_4}$

Lewis Dot Diagram:

• Carbon (C) is central, has 4 valence electrons.
• Four Chlorine (Cl) atoms, each with 7 valence electrons.
• C forms 4 single bonds with Cl (sharing 1 electron pair each).
• Each Cl has 3 lone pairs (6 electrons) after bonding.

(Diagram: C in center, 4 Cl atoms around it, each Cl with 3 lone pairs, C - Cl bonds as electron pairs.)

Naming:

• Prefix for C: “carbon” (1 atom, no prefix).
• Prefix for Cl: “tetra-” (4 atoms) + “chlorine” → “tetrachloride”.
• Name: Carbon Tetrachloride

5. $\boldsymbol{CS_2}$

Lewis Dot Diagram:

• Carbon (C) is central, has 4 valence electrons.
• Two Sulfur (S) atoms, each with 6 valence electrons.
• C forms 2 double bonds with S (sharing 2 electron pairs each, total 4 electrons per bond).
• Each S has 2 lone pairs (4 electrons) after bonding (since 6 - 4 = 2 lone pairs? Wait: S has 6 valence e⁻, in double bond, it shares 4 e⁻ (2 pairs), so 6 - 4 = 2 lone pairs? Wait, no: double bond is 4 e⁻ (2 pairs) shared. So S has 6 - 4 = 2 lone pairs? Wait, no: 6 valence e⁻, in double bond, it contributes 2 e⁻ to the bond, so total shared is 4 (2 from C, 2 from S). So S has 6 - 2 = 4? Wait, no: Lewis structure for $CS_2$ is linear, C double - bonded to two S atoms, each S has 2 lone pairs (4 electrons). Wait, C has 4 valence e⁻, forms two double bonds (each double bond is 4 e⁻), so 4 + 4 + 4 = 12? Wait, C: 4, each S: 6, total valence e⁻: 4 + 6×2 = 16. Double bonds: each double bond is 4 e⁻, two double bonds: 8 e⁻. Lone pairs: each S has (6 - 4) = 2 lone pairs (4 e⁻ per S), so 2×4 = 8 e⁻. Total: 8 + 8 = 16. Correct.

(Diagram: C in center, double - bonded to two S atoms (linear), each S with 2 lone pairs.)

Naming:

• Prefix for C: “carbon” (1 atom, no prefix).
• Prefix for S: “di-” (2 atoms) + “sulfur” → “disulfide”.
• Name: Carbon Disulfide

6. $\boldsymbol{H_2O_2}$

Lewis Dot Diagram:

• Two Oxygen (O) atoms bonded to each other (single bond), each O bonded to one H.
• O has 6 valence e⁻, H has 1.
• Structure: H - O - O - H.
• Each O has 2 lone pairs (4 e⁻) and 2 bonding pairs (1 with H, 1 with O).
• Each H has 1 bonding pair (with O).

(Diagram: H - O - O - H, each O with 2 lone pairs.)

Naming:

• Common name: Hydrogen Peroxide (systematic: Dihydrogen Dioxide, but “hydrogen peroxide” is standard).

7. $\boldsymbol{CHCl_3}$

Lewis Dot Diagram:

• Carbon (C) is central, has 4 valence e⁻.
• Bonded to 1 H, 3 Cl atoms.
• C - H (single bond, 2 e⁻), C - Cl (three single bonds, each 2 e⁻).
• H has 0 lone pairs, each Cl has 3 lone pairs (6 e⁻).
• C has no lone pairs (4 bonds, 8 e⁻).

(Diagram: C in center, H and three Cl atoms around it, Cl with 3 lone pairs each, C - H and C - Cl bonds.)

Naming:

• Prefix for C: “carbon” (1 atom, no prefix).
• Prefix for H: “mono-” (1 atom, but “mono-” is often omitted for H) + “hydrogen”.
• Prefix for Cl: “tri-” (3 atoms) + “chlorine” → “trichloride”.
• Name: Chloroform (common name) or Trichloromethane (systematic).

8. $\boldsymbol{C_2H_5Cl}$

Lewis Dot Diagram:

• Two C atoms bonded to each other (single bond, central).
• First C: bonded to 3 H atoms and the second C.
• Second C: bonded to 2 H atoms and 1 Cl atom.
• Valence e⁻: Each C has 4, H has 1, Cl has 7.
• Bonds: C - C (single, 2 e⁻), C - H (single, 2 e⁻), C - Cl (single, 2 e⁻).
• Lone pairs: Cl has 3 lone pairs (6 e⁻), H has 0, C has 0 (all bonds).

(Diagram: C - C in center, first C: 3 H, second C: 2 H and 1 Cl, Cl with 3 lone pairs.)

Naming:

• Parent chain: 2 C atoms (ethane).
• Substituent: Cl (chloro) on the second C (or first, since symmetric).
• Name: Chloroethane (or Ethyl Chloride).

Final Answers (Names):

1. Carbon Tetrafluoride
2. Selenium Difluoride
3. Ammonia (Nitrogen Trihydride)
4. Carbon Tetrachloride
5. Carbon Disulfide
6. Hydrogen Peroxide
7. Chloroform (Trichloromethane)
8. Chloroethane (Ethyl Chloride)