Draw the best Lewis structure for Cl3. What is the formal charge on the central Cl atom? A) -1 B) 0 C) +1 D) +2 E) -2 A -1 B. 0 C+1 D.+2 E: 2
The Correct Answer and Explanation is:
The best Lewis structure for Cl₃ (trichlorine molecule) involves three chlorine atoms. Since chlorine typically forms one bond and has seven valence electrons, we must consider how three chlorine atoms can be arranged to minimize formal charges and follow the octet rule as much as possible.
Structure:
We place one chlorine atom in the center and the other two on the sides. The structure is:
Cl–Cl–Cl
This means each outer Cl atom forms a single bond with the central Cl atom. Each chlorine atom has 7 valence electrons. Bonding uses 1 electron from each Cl per bond. Here’s the breakdown:
- Outer Cl atoms each form one bond and retain 6 non-bonding electrons (3 lone pairs).
- The central Cl atom forms two bonds (one with each outer Cl) and retains 4 non-bonding electrons (2 lone pairs).
Now let’s calculate formal charges using the formula:
Formal charge = Valence electrons – (Nonbonding electrons + ½ Bonding electrons)
For the central Cl atom:
- Valence electrons = 7
- Nonbonding electrons = 4
- Bonding electrons = 4 (2 bonds × 2 electrons)
Formal charge = 7 – (4 + 2) = +1
For each outer Cl atom:
- Valence electrons = 7
- Nonbonding electrons = 6
- Bonding electrons = 2 (1 bond)
Formal charge = 7 – (6 + 1) = 0
Final Answer: C) +1
Explanation:
The Cl₃ molecule is a neutral triatomic species composed entirely of chlorine atoms. It is uncommon and unstable but theoretically possible. The central Cl atom shares electrons with both outer Cl atoms, but since each Cl wants to keep its full octet, only single bonds are formed. This causes the central Cl to be slightly electron-deficient, leading to a formal charge of +1. The outer atoms are satisfied with lone pairs and have no formal charge. The best Lewis structure minimizes formal charges overall and obeys the octet rule as closely as possible.
