同学们都知道．元素的化合价是一种元素一定数目的原子跟其他元素一定数目的原子化合的性质．它反映了元素的原子间相互结合时的数量关系。元素化合价的知识是初中化学的主要内容之一．但它具有一看就会，一丢就忘．一写就错的特点。因此．它也是初中化学的难点。为了帮助同学 The classmates all know. The valence of an element is the combination of a certain number of atoms of a certain element with a certain number of atoms of other elements. It reflects the quantitative relationship between the atoms of the elements when they are joined together. The knowledge of element valence is one of the main contents of Junior Chemistry. But it will have a look and forget it. Wrote the wrong features. therefore. It is also a difficulty for junior high school chemistry. To help students