Iron: bond enthalpies in gaseous diatomic species

The bond energy in the gaseous diatomic species FeFe is 75 ±17 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 FeX bond enthalpies. All values are quoted in kJ mol-1. Each formula in the table (FeO, FeF, and so on) is a link - select these to see visual periodicity representations for bond enthalpies involving iron to elements of your choice.

Period 1

FeH             FeHe
180 ±25              

Period 2

FeLi FeBe FeB FeC FeN FeO FeF FeNe
          390.4 ±17.2    

Period 3

FeNa FeMg FeAl FeSi FeP FeS FeCl FeAr
      297 ±25   322 about 351  

Period 4

FeK FeCa FeGa FeGe FeAs FeSe FeBr FeKr
      210.9 ±29     247 ±96  

Period 5

FeRb FeSr FeIn FeSn FeSb FeTe FeI FeXe

Period 6

FeCs FeBa FeTl FePb FeBi FePo FeAt FeRn

Period 7

FeFr FeRa            


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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