摘要
本文提出卤化物化学键的稳定度的概念,用于衡量卤化物化学键的稳定性。给出了键稳定度公式S_(AB)=E_(AE)/(r_(AB)|x_A—x_B|),S_(AB)为键稳定度,E_(AB)为键能,r_(AB)为键长,x_A和x_B为两原子的电负性。卤化物建稳定度的物理意义是:在平衡状态下,卤化物单键上两原子的单位电负性差、单位键长的键能。用公式计算了52个金属离子卤化物的键稳定度,得到260个数据,用于硬软酸的定量分类。结果表明,用其中的(S_F—S_1)值能有效地把硬酸、交界酸、软酸分开,S_F—S_I>10为硬酸,-10<S_F—S_I<10为交界酸、S_F—S_I<-10为软酸;硬酸的S值为F>Cl>Br>I,软酸的S值为F<Cl<Br<I。这一结果与Pearson根据实验总结的分类一致,卤化物的键稳定度在元素周期表的主族元素中表现出良好的规律性。
A new concept named 'halide bond stability', S_(AB), is proposed to estimate the degree of bond stability of halides. The formula for calculating the halide bond stability is given as S_(AB)=E_(?)/(r_(?)|x-x_(?)|), where E_(AB) is bond energy, r_(AB) is bond length, and x(?) and x(?) are electronegativities of atom A and B respectively. The physical explanation for halide bond stability is the bond energy per unit bond length per unit electronegativity difference of the two atoms of the single bond in equilibrium state. The halide bond stability for 52 metal ions has been calculated by using the above-mentioned formula, and 260 values have been obtained. The data are used for the quantitative classification of acids as hard or soft. The result shows that hard acids, border line acids and soft acids can be distinguished by (S_F-S_I) clearly, that is, S_F-S_I>10 for hard acids, -10<S_F-S_I<10 for border-acids, and S_F-S_I<-10 for soft acids; the values of S are F>Cl>Br>I for hard acids, and F<Cl<Br<I for soft acids. This result agrees with the classification reported by Pearson. The halide bond stability of the main group elements in the Periodic Table increases on traversing the Table for the group oxidation state, and decreases on descending a column in the Table for The same oxidation state.
出处
《广州化学》
CAS
1989年第4期17-26,共10页
Guangzhou Chemistry
