化学系专业外语课件6.Chapter 11 Electron Pair Repulsion and Molecular Geometry教学讲义.ppt

Electron Pair Repulsion and Molecular Geometry (电子对排斥和分子的几何构型) bond pair 成键电子对 boundary surface 界面 contract 收缩 coplaner 同平面的 covalent bond 共价键 depict 描述 distort 变形, 扭曲 electron pair 电子对 electrostatic repulsion 静电排斥 equatorial position 赤道位 hybridized orbital 杂化轨道 linear 直线形的 localized 定域 lone pair 孤对电子 molecular geometry 分子几何结构 octahedron 八面体 orientation 取向, 定向 planer 平面的 polar position 极位 polarity 极性 square pyramid 四方锥 tetrahedron 四面体 triangular 三角形 trigonal pyramid 三角锥 trigonal bipyramid 三角双锥 valence level 价电子层 The orientation that a set of atoms assumes in the formation of a given molecule may be explained qualitatively on the basis of electrostatic repulsions between electron pairs. In the application of this concept, attention is directed to the valence level of the central atom of the molecule, and the diagrams for the examples that follow show only the electrons of this level of the central atom. Mercury has two electrons in its valence level (6s2); these are used to form two covalent bonds with two chlorine atoms in the mercuric chloride molecule, HgCl2. The molecule is linear: The HgCl2 molecule assumes a configuration such that the two electron-pair bonds are as widely separated as possible , thus minimizing the electrostatic repulsion between them. Molecules of the type B:A:B are invariably linear; berylium, zinc, cadmium, and mercury form such molecules. The boron trifluoride molecule is triangular and planar. Each of the bond angles of the molecule is 120o, and this arrangement provides the greatest possible separation between the three electron pairs. In the methane molecule, CH4, the central carbon atom has four pairs of e