Chapter 9 Chemical Bonding andMolecular Structure
1 Chapter 9 Chemical Bonding and Molecular Structure
What is chemical bonding?Chemical bonds refer to the main, direct, andstrong forces between atoms and ionsWhat chemical bonds types are there?covalentbondsionic bondsmetal bonds
2 What is chemical bonding? Chemical bonds refer to the main, direct, and strong forces between atoms and ions. What chemical bonds types are there? • covalent bonds • ionic bonds • metal bonds
Three objectives:Covalent bonding and atomic crystalslonic bonds andionic substancesIntermolecularforcesandmolecularcrystals
3 Three objectives: ◼ Covalent bonding and atomic crystals ◼ Ionic bonds and ionic substances ◼ Intermolecular forces and molecular crystals
9-1 Covalent bondingand atomic crystals9-1-1 Valence bonding theory9-1-2Hybridization9-1-3Valenceshell electronpairrepulsion(VSEPR)9-1-4 Molecular Orbit Theory
4 9-1 Covalent bonding and atomic crystals 9-1-1 Valence bonding theory 9-1-2 Hybridization 9-1-3 Valence shell electron pair repulsion （VSEPR） 9-1-4 Molecular Orbit Theory
Ouestion1:How do molecules form from atoms ofelements withthesameor closeelectronegativity?Why the hydrogen molecule exists as H,instead of H3 or any other molecularformula?
5 Question 1: How do molecules form from atoms of elements with the same or close electronegativity? Why the hydrogen molecule exists as H2 instead of H3 or any other molecular formula?
9-1-1 Valence bonding theory1916年，路易斯提出经典共价键理论；1927年，海特勒-伦敦等用量子力学处理氢分子结构A/EAEs↑↑0↑R/pmRo=87pmFigure9-1RelationshipbetweenHenergyanditsnucleusdistance.6
6 9-1-1 Valence bonding theory 0 E/eV R0=87pm R/pm Es EA Figure 9-1 Relationship between H2 energy and its nucleus distance. 1916年, 路易斯提出经典共价键理论; 1927年, 海特勒-伦敦等用量子力学处理氢分子结构
xPx-spx(b)(c)(a)Figure9-2SchematicsofHCIbondingThe bonding atomic orbitals must overlap as muchaspossible,thatis,they must overlapinthemaximumwavefunctiondirection
7 - + + z x px-s (a) - + + z x px (b) s - + + z x px (c) s Figure 9-2 Schematics of HCl bonding. The bonding atomic orbitals must overlap as much as possible, that is, they must overlap in the maximum wave function direction
价键理论（VB法）·具有自旋方向相反的单电子的原子相互接近时，单电子可以配对构成共价键重叠越多，形成的共价键越稳定，即原子轨道最大重叠原理X
8 价键理论(VB法) • 具有自旋方向相反的单电子的原子相互 接近时,单电子可以配对构成共价键. • 重叠越多，形成的共价键越稳定，即原 子轨道最大重叠原理
共价键的特征1.具有饱和性（所形成的共价键数目取决于它所具有的未成对电子数2.具有方向性（形成共价键时，原子间总是尽可能沿着原子轨道最大重叠的方向成键
9 共价键的特征 1. 具有饱和性（所形成的共价键数目取决于 它所具有的未成对电子数） 2. 具有方向性（形成共价键时，原子间总是 尽可能沿着原子轨道最大重叠的方向成键）
two types of covalent bonds键型-sigma(o) bonds and pi(π) bonds键，元键The line through the two nucleus is calledinternuclear axis( bond axes键轴) x.sigma symmetrical orbital, such as ys,px,dx2-y2,Vdz2,pi symmetrical orbital, such as Vpy, Vpz,Vdxy, dyz, dxz10
10 two types of covalent bonds键型— sigma(σ) bonds and pi() bonds σ键，π键 The line through the two nucleus is called internuclear axis( bond axes键轴) x. ◼ sigma symmetrical orbital, such as s , px, dx2-y2, dz2; ◼ pi symmetrical orbital, such as py, pz, dxy, dyz, dxz