对化学系的学生来讲,学过分子的对称性,应当具有能较快找出一个已知构型的分子所具有的全部对称元素,并能正确写出其所属点群的符号.要实现这一目标,除课堂学习和模型实习外,必须做适当数量具有启发性能促使积极思考的习题,以训练空间想像能力和立体感.下面一套习题就是为此目的而设计的.实际上它可以看成是对称性问题的一个小小试题库,略加变化又可得到另一套题目. 这套习题可分成两大类第一类给出已知图形所具有的全部对称元素和所属点群. For chemistry students, to learn the symmetry of a molecule, it should be able to find all the symmetry elements of a molecule with a known configuration faster and correctly write the symbol of the point group to which it belongs. This goal, in addition to classroom learning and model practice, must be complemented by the appropriate number of instructive exercises that inspire positive thinking in order to train spatial imagination and stereoscopy. The following set of exercises is designed for this purpose. In fact it can Think of it as a small test question library for symmetry, with a slight change to get another set of questions. The set of exercises can be divided into two broad categories. The first category gives all the symmetry elements and associated point groups that a known graphic has .