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分子中原子间或离子间的强烈的相互作用称为化学键。这种相互作用的强度可以用键能的大小来量度。一般将气态下每断开1摩尔键所需要的能量定义为该键的键能。实际上这个能量变化应称之为键离解能。仅仅对于双原子分子来说,因为其分子中只有一个化学键,其键能可以由键离解能直接确定;对于多原子分子,其分子中存在两种以上的化学键时,每单个键的键能与键离解能可能在数值上相差极大。前者是由热化学实验数据归纳得到的近似的平均值。后者可以利用光谱学实验数据计算。对于少数双原子分子,还有希望根据量子物理学方法作出精确的理论计算。例如,双原子分子H_2,由光谱学实验数据计算出H—H键的离解能是432.00千焦/摩;而H—H键的键能是433.21千焦/摩。二者在数值上相差不大。
The strong intermolecular or intermolecular interactions in molecules are called chemical bonds. The strength of this interaction can be measured by the size of the bond energy. The energy required to disconnect one mole of bond in the gaseous state is generally defined as the bond energy of the bond. In fact, this energy change should be called bond dissociation energy. Only for diatomic molecules, the bond energy of a diatomic molecule can be directly determined by the dissociation of the bond because there is only one chemical bond in its molecule. For polyatomic molecules, where there are more than two types of chemical bonds in the molecule, Key dissociation energy may vary greatly in value. The former is an approximate average derived from thermochemical experimental data. The latter can be calculated using spectroscopic experimental data. For a few diatomic molecules, there is also hope to make accurate theoretical calculations based on quantum physics methods. For example, the diatomic molecule H_2, calculated from the spectroscopic experimental data, shows that the dissociation energy of the H-H bond is 432.00 kJ / mol; and the bond energy of the H-H bond is 433.21 kJ / mol. The two are not much different in value.