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在元素符号周围不同位置的阿拉伯数字,分别有不同的含义。而学生常因分辨不清面导致作业时有差错。为使学生能正确地认识核式,分辨微粒数与所含微粒数的不同,能规范地标出元素的化合价和离子的电荷符号。在初三化学教过“离子”概念之后,我补充一个组合练习题,内容如下: 设R为某元素的符号,它周围的a、b、c、±d、e±和f分别表示什么意思? 在师生共同讨论后作出小结: 正左方的a表示微粒个数; 左下角的b表示该元素原子核内质子数(或核电荷数); 左上角c表示原子量(对高中学生应确切地说表示原子的质量数);
The Arabic numerals in different positions around the element symbols have different meanings. However, students often make mistakes when they do not understand the job. In order to enable students to correctly understand the nuclear-type, the number of differentiated particles and the number of particles contained in can be marked standard valence of the element and the charge sign of ions. After the third-year chemistry taught me the concept of “ion,” I added a combination of exercises that read as follows: Let R be the symbol of an element, what do the surrounding a, b, c, ± d, e ± and f denote ? After a discussion between teachers and students to make a summary: a is the left of the number of particles; the lower left corner of the proton that the number of nuclei in the nucleus (or the number of nuclear charge); upper left c represents the atomic weight (for high school students should be exactly Said that the atomic mass number);