Why doesn't CSCl2 have resonance?

Answer 1

The compound in question is indeed CSCl2, known as thiophosgene. Cesium Chloride is CsCl,

As to the question, resonance occurs when a molecule has two or more possible bond configurations about the same atom, such as with the alternating single and double bonds often depicted in benzene. Although, the resonance hybrid will remain as the most accurate depiction.

In the case of CSCl2 the central carbon atom is double bonded to a sulfur atom and single bonded to two chlorine atoms. There is no other stable configuration. The sulfur atom is not stable with just one single bond and the chlorine atoms, which already have their octets satisfied, will not accept a double bond from the carbon.

Answer 2

CsCl (not CsCl2) is cesium chloride, and like sodium chloride, or potassium chloride, it is an ionic compound and will not show resonance.