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每一种离子晶体的类型得借助于现代科学实验手段(如x射线衍射晶体结构分析)而确定,晶型一经确定便可推导其阳、阴离子的数目。下面以现行统编中学化学教材介绍的NaCl、CsCl离子晶体为例分析这个问题。我们知道,NaCl和CsCl都是以离子键结合的离子化合物。在室温下,它们均以离子晶体的形式存在着。在这两种离子晶体中,阳、阴离子按一定规律在三度空间排列,并隔一定的距离周期性地重复出现这些阳、阴离子的粒子。这种粒子的有规律的空间排列可用空间格子来表示。这种空间格子称为晶格。书中的图3—10和图3—11就是NaCl和CsCl晶格的示意图。在每个晶格的交点上分别由Na~+(或Cs~+)和Cl~-离子占据着。要计算每种晶格中阳、阴离子的数目比,就得计算每种晶格中所含阳、阴离子的实际数目。先讲图3—10的NaCl晶格。Na~+位于它
The type of each ion crystal is determined by means of modern scientific experiments such as X-ray diffraction crystal structure analysis. Once the crystal form is determined, the number of cations and anions can be deduced. The following analysis of this problem is based on the example of NaCl and CsCl ion crystals introduced in the current textbook on middle school chemistry. We know that both NaCl and CsCl are ionically bonded ionic compounds. At room temperature, they all exist as ionic crystals. In these two kinds of ion crystals, the positive and negative ions are arranged in a three-dimensional space according to a certain rule, and these positive and negative ions are periodically repeated at a certain distance. The regular spatial arrangement of such particles can be represented by a spatial lattice. This spatial lattice is called a lattice. Figure 3-10 and Figure 3-11 in the book are schematic representations of the NaCl and CsCl lattices. At the intersection of each lattice, Na+(or Cs~+) and Cl~- ions are occupied. To calculate the ratio of the number of cations and anions in each lattice, the actual number of cations and anions contained in each lattice must be calculated. Let us first discuss the NaCl lattice in Figure 3-10. Na~+ is in it