In chemistry, the bond energy is also called the "mean bond enthalpy" or "average bond enthalpy" and is a measure of the strength of the chemical bond between the atoms concerned.


It is taken as the average of all of the bond dissociation energies of a single type of bond in a given molecule because the bond energies of several different types of bond can vary even in a single molecule. For example in the simple molecule Water there are two O-H bonds and the average bond dissociation energy is taken as the energy required to break both bonds divided by 2. As a result of this the cannot be a fixed bond dissociation energy for a given pair of elements, that is for example the O-H bond in an organic alcohol may have a different dissociation energy to that of water, and as the multiplicity of the bond increases so does the amount of energy required to break it.


This contents of this table are from one of many available on the Internet. 


If you are given a bond dissociation calculation, you will almost certainly be given the appropriate values to use. It is important that you use the values you're given and do not source these from anywhere else unless you have to.


Bond

Energy

kJmol-1

Length

pm

Bond

Energy

kJmol-1

Length

pm

Bond

Energy

kJmol-1

Length

pm

Bond

Energy

kJmol-1

Length

pm

SINGLE BONDS

H-H

432

74

N-H

391

101

Si-H

323

148

S-H

347

134

H-F

565

92

N-N

160

146

Si-Si

226

234

S-S

266

204

H-Cl

427

127

N-P

209

177

Si-O

368

161

S-F

327

158

H-Br

363

141

N-O

201

144

Si-S

226

210

S-Cl

271

201

H-I

295

161

N-F

272

139

Si-F

565

156

S-Br

218

225




N-Cl

200

191

Si-Cl

381

204

S-I

~170

234

C-H

413

109

N-Br

243

214

Si-Br

310

216




C-C

347

154

N-I

159

222

Si-I

234

240

F-F

159

143

C-Si

301

186







F-Cl

193

166

C-N

305

147

O-H

467

96

P-H

320

142

F-Br

212

178

C-O

358

143

O-P

351

160

P-Si

213

227

F-I

263

187

C-P

264

187

O-O

204

148

P-P

200

221

Cl-Cl

243

199

C-S

259

181

O-S

265

151

P-F

490

156

Cl-Br

215

214

C-F

453

133

O-F

190

142

P-Cl

331

204

Cl-I

208

243

C-Cl

339

177

O-Cl

203

164

P-Br

272

222

Br-Br

193

228

C-Br

276

194

O-Br

234

172

P-I

184

246

Br-I

175

248

C-I

216

213

O-I

234

194




I-I

151

266

MULTIPLE BONDS (<tr> = triple bond)

C=C

614

134

N=N

418

122

C<tr>C

839

121

N<tr>N

945

110

C=N

615

127

N=O

607

120

C<tr>N

891

115

N<tr>O

1020

106

C=O

745

123

O=O

498

121

C<tr>O

1070

113




799 in CO2













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