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本文首先指出,从对称类型(点群)来判断分子的极性是极其麻烦的,如根据特征对称要素则能快速而准确地做出判断。这对于有关的教学工作有其实际意义。其次指出,非极性分子的特征对称要素除一般所知的对称中心外,还有高次反轴4,6,8,10等也是特征对称要素。除此之外,并发现如分子本身井无特征对称要素,但其各基矩有对称中心及高次反轴则亦为非极性分子,如C(NO_2)_4,Al(BH_4)_3等就是如此。
This paper first points out that it is extremely troublesome to judge the polarity of a molecule from the symmetry type (point group). For example, according to the characteristic symmetric elements, the judgment can be made quickly and accurately. This is of practical significance to the teaching work involved. Secondly, it is pointed out that the characteristic symmetry elements of nonpolar molecules have high symmetry centers, and the high order anti-axis 4, 6, 8, 10 and so on are also characteristic symmetric elements. In addition, we find that there are no symmetrical elements in the molecule itself, but their base moments have symmetry center and high order anti-axis, which are also non-polar molecules such as C (NO 2) 4, Al (BH 4) 3 That’s it.