化学中化合物种类数问题与数学中的分类计数原理、分步计数原理及排列、组合有密切关系．解决这类问题关键是合理分类、分步,同时注意化合物分子结构的对称性特点,否则容易造成计数的重复与遗漏．用数学工具解决这类问题,既可增强应用数学的意识,提高运用数学知识分析解决化学问题的能力,又可将不同学科知识联系起来相互促进理解与学习． The problem of the number of compounds in chemistry is closely related to the principle of classification and counting in mathematics, the principle of step-by-step counting, and the arrangement and combination. The key to solving such problems is reasonable classification and step-by-step, and at the same time pay attention to the symmetry characteristics of the molecular structure of the compound, otherwise it is easy to cause repetition and omission of counting. The use of mathematical tools to solve such problems can not only enhance the awareness of applied mathematics, improve the ability to use mathematical knowledge to analyze and solve chemical problems, but also link different disciplines of knowledge to promote mutual understanding and learning.