唯物辩证法原理在金属性教学中的应用

Teaching Practice in the Metallicity of Metal Elements Based on Materialist Dialectics

金属元素的金属性是无机化学教学中的一个难点。金属元素在不同情况下表现出的失电子能力不同,这就需要我们运用唯物辩证法原理中的观点和方法来剖析金属元素的金属性。根据金属元素的存在形式和反应条件,采用不同的金属性衡量标准,做到具体问题具体分析的原则。当金属元素处于气态自由原子时,采用电离能(I)作为金属性的衡量标准。当金属单质在干态下与非金属单质反应时,采用产物的ΔfHm^(ϴ)和ΔfGm^(ϴ)作为金属性的衡量标准。当金属单质在水溶液中发生反应时,采用电对(M^(n+)/M)的标准电极电势(φ^(ϴ))作为金属性的衡量标准。最后,还需要正确看待热力学和动力学之间的关系。热力学衡量标准只表明金属元素失电子趋势;若要解释实际的反应速率,需要结合动力学影响因素。

Metallicity is one of major difficulties in inorganic chemistry.The metal element has various ability of losing its electrons in various conditions,so we should analyze the metallicity by using some viewpoints and methods of materialist dialectics.The right evaluation criterion of metallicity is chosen according to actual condition on the basis of the particularity of contradiction.Ionization energy(I)is adopted to evaluate the metallicity when the metal element exists in a free-atom state.ΔfHm^(ϴ) or ΔfGm^(ϴ) is employed to evaluate the metallicity when the elemental metal reacts with the nonmetal in dry condition.The standard electrode potential(φ^(ϴ))is taken to evaluate the metallicity when the elemental metal reacts with the oxidant in aqueous solution.Finally,it is essential to understand the relationship between thermodynamics and dynamics.Thermodynamic criteria(I,ΔfHm^(ϴ),ΔfGm^(ϴ),and φ^(ϴ))only indicate the ability of losing electrons,and the reaction rate is depended on actual dynamic factors.