文档介绍：第十章
共价键与分子间力
Covalent Bond and Intermolecular Forces
物质结构知识复习
构成物质的基本单元是什么?这些基本单元由什么组成?靠何种力量结合?
molecule or crystal is the basic structure unit of a substance.
molecule or crystal consists of atoms or ions.
bond is a strong interaction force between two adjacent atoms or ions .
The Types of Chemical bonds
The chemical bond was due to sharing electrons between two atoms.
Ionic Bond 离子键
The chemical bond was due to of the strong electrostatic attraction between cation and anion.
Covalent Bond 共价键
Metallic Bond 金属键
Bonding in which the bonding electrons are relatively free to move throughout the three dimensional structure
物质的存在状态有哪几种?为何?
Attractive forces between molecules were called intermolecular force.
分子的空间构形由何种因素决定?
Lewis Structure and Octet Rule
1s22s22p5
A rule stating that bonded atoms tend to possess or share a total of eight valence shell electrons
Octet Rule
§1 现代价键理论 Valence Bond Theory (VB)
F
F
+
F
F
(1) Can explain the saturation of bond
(2)Can not explain the directionality of bond
(3)can not explain the molecules in which an atom has less or more than an octet
Octet Rule
BF3
1s22s22p1
B
F
1s22s22p5
↑↓
↑↓
↑
↑
2px 2py 2pz
Boron trifluoride
B
F
F
F
e > 8
Cl
Cl
P
Cl
Cl
Cl
e < 8
1926年 Heitler 和 London 用量子力学研究氢分子的形成,解释共价键的本质
一氢分子的形成
1. H2的成键状态
根据量子力学计算:两个氢原子接近时,核间距达74 pm时,两核间电子云密度增加,体系的能量下降,称为基态(ground state)或吸引态。此时两个氢原子的电子处于自旋反平行状态。
Ψ1 2 + Ψ2 2
After electron cloud overlap
(ψ1+ψ2) 2= ψ1 2+ 2ψ1ψ2+ ψ2 2
Before electron cloud overlap
ψ1 2+ ψ2 2
(ψ1+ψ2) 2> ψ1 2+ ψ2 2
represent concentrated electron cloud between two H nuclei
attraction between nucleus and electron;
repulsion between two nuclei
two atoms can bined through “bridge ” of concentrated electron cloud
ψ2
ψ1
↓
↑
r0