无机化学无机化学英文PPT (8).ppt

9.4 Molecular crystals1.Molecular dipole moment and polarizabilityNonpolar covalent bondpolar covalent bondAtomic nuclearCenter of positive chargerCenter of negative charger1.The dipole moment of the molecule():Used to quantitatively express the polarity of a polar molecule.Polar molecules 0Nonpolar molecule =0Diatomic molecule：Polyatomic molecules:same nuclear:q is the electric charge on the pole,l is the length of the dipole.Heteronuclear:HX偶极矩偶极矩 Dipole moent 分子的极性及对极性强弱的定量判断是通分子的极性及对极性强弱的定量判断是通过测定分子的偶极矩来实现的。过测定分子的偶极矩来实现的。偶极矩偶极矩 u=0的共价键叫非极性共价键，的共价键叫非极性共价键，偶极矩偶极矩 u 0的共价键叫极性共价键；的共价键叫极性共价键；偶极矩偶极矩 u=0的分子叫非极性分子，的分子叫非极性分子，偶极矩偶极矩 u 0的分子叫极性分子的分子叫极性分子Dipole moment to quantitative measure the molecular polarity and its strength,expressed as u.covalent bond when u=0 is called nonpolar covalent bondwith u 0 is called polar covalent bondcovalent bond molecule when u=0 is called nonpolar molecule,when u 0 is called polar moleculeDipole moment of the molecule (10-30 Cm)to quantify the degree of deformation of a molecule,in which,its deformability refers to the displacement of the positive and negative center(from overlap to misoverlap,and from small to large dipole).External cause:the stronger the applied electric field,the more severe the molecular deformation;Internal cause:The larger the molecule volume,the greater the molecular deformation.Factors influencing the degree of molecular deformability2.Molecular polarizabilityMolecular polarizability (10-40Cm2 V1)