Chlorine: bond enthalpies in gaseous diatomic species

The bond energy in the gaseous diatomic species ClCl is 242.580 ±0.004 kJ mol-1.

The following values refer to neutral heterodiatomic molecules in the gas phase. These numbers may well differ considerably from, say, single bond energies in a solid. All values are given in kJ mol-1.

Table of diatomic ClX bond enthalpies. All values are quoted in kJ mol-1. Each formula in the table (ClO, ClF, and so on) is a link - select these to see visual periodicity representations for bond enthalpies involving chlorine to elements of your choice.

Period 1

ClH             ClHe

Period 2

ClLi ClBe ClB ClC ClN ClO ClF ClNe
469 ±13 388.3 ±9.2 536 397 ±29 333.9 ±9.6 269.1 256.23  

Period 3

ClNa ClMg ClAl ClSi ClP ClS ClCl ClAr
412.1 ±8 327.6 ±2.1 511.3 ±0.8 406 289 ±42 277.0 242.580 ±0.004  

Period 4

ClK ClCa ClGa ClGe ClAs ClSe ClBr ClKr
433.0 ±8 409 ±9 481 ±13 about 431 448 322 217.53 ±0.29  

Period 5

ClRb ClSr ClIn ClSn ClSb ClTe ClI ClXe
427.6 ±8 406 ±13 439 ±8 414 ±17 360 ±50   211.3 ±0.4 6.7

Period 6

ClCs ClBa ClTl ClPb ClBi ClPo ClAt ClRn
448 ±8 436.0 ±8.4 372.8 ±2.1 301 ±29 301 ±4      

Period 7

ClFr ClRa            
  343 ±75            


I am grateful to Professor J.A. Kerr (University of Birmingham, UK) for the provision of the bond strengths of diatomic molecules data.

The values given here are at 298 K. All values are quoted in kJ mol-1. Generally, these data were obtained by spectroscopic or mass spectrometric means. You should consult reference 1 for further details. A note of caution: the strength of, say, the C-H bond in the gaseous diatomic species CH (not an isolable species) is not necessarily, the same as the strength of a C-H bond in, say, methane.

The strongest bond for a diatomic species is that of carbon monoxide, CO (1076.5 ± 0.4 kJ mol-1). The strongest bond for a homonuclear diatomic species is that of dinitrogen, N2 (945.33 ± 0.59 kJ mol-1).


  1. J.A. Kerr in CRC Handbook of Chemistry and Physics 1999-2000 : A Ready-Reference Book of Chemical and Physical Data (CRC Handbook of Chemistry and Physics, D.R. Lide, (ed.), CRC Press, Boca Raton, Florida, USA, 81st edition, 2000.

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chlorine atomic number