Thiophosgene (CSCl2) is a reddish-orange fuming liquid primarily used in organic chemistry as a versatile reagent to synthesize isothiocyanates, thioureas, and thiocarbonates. The picture below shows its Lewis structure.

How to draw the lewis structure of CSCl2?

Step 1: Identify the central atom

Electronegativity: C < S < Cl; C is the central atom

Skeleton arrangement: Cl?C?Cl, with S bonded to C

Step 2: Form initial σ bonds

Skeleton: Cl?C?Cl, with S attached to C

Total of 3 σ bonds; electrons used: 3 × 2 = 6e?

Remaining electrons: 24 ? 6 = 18e?

Step 3: Fill in lone pairs on terminal atoms

Each Cl atom needs to satisfy the octet rule; add 3 lone pairs to each: 2 Cl atoms consume 2 × 6 = 12e?

Remaining electrons: 18 ? 12 = 6e?; assign all to S → S temporarily has 3 lone pairs

At this stage, C has only 6 valence electrons (from 3 single bonds) and does not satisfy the octet rule; a double bond is required.

Step 4: Form a double bond to satisfy the octet for central C

Convert one lone pair on S into a C=S double bond: C=S double bond; two C–Cl single bonds

Bonding arrangement: C=S, C?Cl, C?Cl

Step 5: Distribute all lone pairs and verify the octet rule

S: Double bond uses 2e?; 2 lone pairs remain (4e?)

Each Cl: Single bond; 3 lone pairs each (6e?)

C: Double bond + two single bonds; total of 8 electrons; satisfies the octet rule