物质结构和元素周期律是化学的重要理论知识,通过学习这部分知识可以使学生深入理解已学元素化合物知识。本章以碱金属元素和卤族元素为代表元素介绍同主族元素性质的相似性和递变性,以第三周期元素为例介绍同周期元素性质的递变规律,由此归纳、总结出元素周期律,为学生今后选 The material structure and the periodic law of elements are important theoretical knowledge of chemistry. By studying this part of knowledge, students can gain a deep understanding of the knowledge of elemental compounds already learned. In this chapter, the similarities and degeneracies of the elements of the same main group are introduced by taking the alkali elements and the halogen elements as the representative elements. The third periodic element is taken as an example to introduce the regularity of the elements of the same periodicity, Law, the future for the students election