The trichloromethyl free radical is a highly reactive and unstable intermediate, the picture below is its lewis structure.

Step 1: Calculate total valence electrons

C: 4 valence electrons

Cl: 7 × 3 = 21

Total valence electrons: 4 + 21 = 25 e?

The total number of electrons is odd; there is one unpaired electron.

Step 2: Determine the central atom and bonding skeleton

C has lower electronegativity and serves as the central atom;

Three C–Cl single bonds; skeleton: central C bonded to three Cl atoms.

Step 3: Construct the σ-bond skeleton

Three C–Cl single bonds; bonding electrons: 3 × 2 = 6 e?

Remaining electrons: 25 - 6 = 19 e?

Step 4: Fill in lone pairs for chlorine atoms

Each Cl atom forms a single bond and requires three lone pairs (6 e?) to satisfy the octet rule.

Total lone pair electrons for three Cl atoms: 3 × 6 = 18 e?

Remaining electrons after allocation: 19 - 18 = 1 e?

Step 5: Arrange the unpaired electron

Place the single remaining electron on the central C atom.

Verification of total electrons: Bonding (6) + Cl lone pairs (18) + C unpaired electron (1) = 25 e?; matches the total valence electron count.