1、第八章第八章 分子结构与晶体结构分子结构与晶体结构(1)序言序言一、化学键一、化学键1 离子键离子键(本质、特征、强弱、离子半径本质、特征、强弱、离子半径)2 共价键共价键(本质、特征、强弱、共价半径本质、特征、强弱、共价半径)3 分子构型分子构型(价电子对互斥理论价电子对互斥理论)4 杂化轨道理论杂化轨道理论5 分子轨道理论分子轨道理论二、二、分子间力和氢键分子间力和氢键1 分子间力分子间力2 氢键氢键三、晶体结构三、晶体结构1 晶体的特征晶体的特征2 晶格和晶胞晶格和晶胞3 晶体的基本类型晶体的基本类型Questions?Why is calcium phosphate so rigid
2、that nature has adopted it for the formation of bones?Can we make better bones?(强离子强离子键键)Why is it so difficult to make compounds from the nitrogen in air?Can we find an easy way?(强共价键强共价键)How can we explain the ability of hemoglobin to form a loosely bonded compound with oxygen,transfer it to anoth
3、er part of the body,and then release it in response to a metabolic need?(配位键配位键)序言序言：原子怎样结合成为分子？原子怎样结合成为分子？化学键化学键 离子键离子键 金属键金属键 分子的形状？分子的形状？分子构型分子构型价电子对互斥理论价电子对互斥理论 分子怎样组成物质材料？分子怎样组成物质材料？分子间作用力分子间作用力 固体材料的结构？固体材料的结构？晶体结构晶体结构无定型结构无定型结构Link1、离子键、离子键(Ionic Bonds)Lewis结构式和八隅体规则结构式和八隅体规则 离子键及其特点离子键及其特点 离
4、子键强度与晶格能离子键强度与晶格能 离子化合物的性质离子化合物的性质 Lewis 结构式结构式,价电子（价电子（Valence electrons）HHe:NO:ClKMg:Ne:K+:Cl K+:Cl:失失或或得得电子电子 八隅体规则八隅体规则(主族主族)Loss or gain electrons octet rule为什么惰性气体稳定？为什么惰性气体稳定？ns2np6 八电子层结构八电子层结构 离子键及其特点：离子键及其特点：定义定义：正负离子间的静电吸引力叫做离子键。：正负离子间的静电吸引力叫做离子键。特点特点：既没有方向性，也不具饱和性。：既没有方向性，也不具饱和性。K+:Cl K+
5、:Cl:NaCl 晶体晶体离子键强度与晶格能离子键强度与晶格能：定义定义：晶格能表示相互远离的：晶格能表示相互远离的气态气态正离子和负离子结正离子和负离子结合成合成 1 mol 离子晶体离子晶体时所释放的能量，或时所释放的能量，或1 mol 离子晶离子晶体解离成自由气态离子时所吸收的能量。（体解离成自由气态离子时所吸收的能量。（A measure of the attraction between ions is lattice enthalpy,the enthalpy change per mol of formula units when a solid is broken up to
6、a gas of widely separated ions.）（取其绝对值）如：（取其绝对值）如：Ca2+(g)+2Cl-(g)CaCl2(s)H=U=2260.kJ/mol晶格能（晶格能（U）(Lattice Enthalpies)离子键强度与晶格离子键强度与晶格能：能：Born-Lande 公式公式U =-Ve Z1Z2/r 其中：其中：Ve 为正负离子间吸引力和排斥力达平衡时，体系的为正负离子间吸引力和排斥力达平衡时，体系的位能；位能；Z1、Z2 分别为正负离子的电荷数；分别为正负离子的电荷数；r为正负离子间为正负离子间距。距。the closer the center of char
7、ge and the greater the charges,the stronger will be the interaction。Born-Haber 循环计算循环计算U（自学，第（自学，第11章，章，p区元素）区元素）生成焓生成焓晶格能晶格能晶格能晶格能生成焓生成焓离子型卤化钠的生成焓和晶格能离子型卤化钠的生成焓和晶格能电子亲核能电子亲核能解离能解离能升华热升华热+电离能电离能离子化合物的性质离子化合物的性质(The Properties of Ionic Compounds)高熔点高熔点 High melting points 高沸点高沸点 High boiling points 易
8、脆性易脆性 Brittleness 溶解性溶解性 Some are soluble,some not.例例 Ca3(PO4)2：骨头的主要成分骨头的主要成分The doubly charged small Ca2+ions,and the triply charged PO43-ions attract one another very strongly and clamp together to form a rigid,insoluble solid.(not completely insoluble,osteoporosis，骨质疏松症，骨质疏松症)2、共价键、共价键(Covalent
9、Bonds)从原子到分子从原子到分子(from atoms to molecules)八隅率与八隅率与Lewis结构结构(The octet rule and Lewis structure)双原子分子双原子分子多原子分子多原子分子共振杂化共振杂化形式电荷形式电荷例外例外 广义八隅率广义八隅率(Expended valence shells)Lewis 酸碱酸碱(Lewis acids and bases)共享电子对共享电子对Nonmetals form covalent bonds to one another by sharing pairs of electrons八隅率与八隅率与Lew
10、is结构结构 The octet rule and Lewis structure The octet rule:In covalent bond formation,atoms go as far as possible toward completing their octet by sharing electron pairs.The valence of an element is the number of covalent bonds of the element forms.(饱和性饱和性)Lone pairs of electrons,pairs of valence elec
11、trons not involved in bondng.(双原子分子中，仅双原子分子中，仅H2无孤对无孤对)A Lewis structure shows the arrangement of valence electrons as shared pairs(line)and lone pairs(dots)多原子分子片的结构多原子分子片的结构The structures of polyatomic species Choose the atom with the lowest ionization energy(electronegativity)to be the central at
12、om.Arrange the atoms symmetrically around the central atom.For example,SO2 is OSO.例例1 HCNValence electrons:1+4+5=10,five pairs.C,lower ionization energy than N,C is central atom H:C:N:H:C:N:或或 H-C N:Suggested steps:a.Determine the number of valence electrons.*Each atom provide all its valence electr
13、ons (only outshell ns and np electrons are considered for main group elements)*a negative charge *a positive charge+b.Write the chemical symbols of the atoms in the arrangement that shows which bonds are formed.The less electronegative element is usually the center atom.c.Distribute the electron in
14、pairs to achieve octet rule.Elements in period 3 and below could have more than 8 electrons in the valence shell.增增减减电离能数据电离能数据p1,失去失去p电子，易电子，易p轨道半满，轨道半满，p3,稳定稳定趋势趋势(与原子与原子半径相反半径相反)Suggested procedure to distribute electrons:a.Put one pair between each pair of atom.b.Put enough pair on the central a
15、tom so that it can achieve octet.c.Distribute the remaining electron pair as evenly as possible to the surrounding atoms to achieve octet.*If octet is not achieved change the electron lone pairs on the central atom to bonding pairs.*If there are some electron pairs left after octet is achieved for e
16、very atom,then put the extra electron pair at the central atom.*Elements in period 3 or below may not follow the octet rule.Additional Lewis structures could also be drawn by change the electron lone pairs on the terminal atoms to bonding pairs.共振结构共振结构(Resonance structure)For some molecules or ions
17、,more than one Lewis structure can be drawn.e.g.OCOOOCOOOCOOCO32-benzeneThe blending of structures with the same arrangements of atoms but different arrangements of electrons.It spreads multiple bond character over a molecular and also lower its energy.In this case,neither one of Lewis structures ca
18、n adequately represent the structure of the molecules.The actual structure is taken to be a blend of all the feasible structures.The concept of blend is called resonance and is indicated by a double-headed arrow.形式电荷形式电荷(formal charge,FC)FC=V (L+1/2S)=自由原子价电子数自由原子价电子数-孤对电子数孤对电子数 (成键电子数成键电子数)=#of val
19、ence electron 2#of lone pairs#of bondsAn indication of the extent to which atoms have gained or lose electrons in the process of covalent bond formation.Lowest FC,lowest energy.例例CO2N2ONCO-八隅率例外八隅率例外,Radicals 例 NO:N=O It is one of neurotransmitters.(神经传递者神经传递者)广义八隅率广义八隅率(Expended valence shells)空的空的
20、d轨道轨道 足够的原子尺寸足够的原子尺寸第第3周期及以后的元素周期及以后的元素Lewis 酸碱酸碱(Lewis acids and bases)A Lewis acid is an electron pair acceptor;A Lewis base is an electron pair donor.They react to form a Lewis acid-base complex.共价键的形成过程：共价键的形成过程：键（头碰头）键（头碰头）The overlap of orbitals to form covalent bonds.(a)The bond in H2 results
21、 from the overlap of two 1s orbitals from two H atoms.(b)The bond in HCl results from the overlap of a 1s orbital of H and one of the lobes of a 3p orbital of Cl.(c)The bond in Cl2 results from the overlap of two 3p orbitals from two Cl atoms.HF的生成的生成 键：键：p轨道（肩并肩）轨道（肩并肩）共价键的主要特点共价键的主要特点是具有是具有饱和性和方向性
22、饱和性和方向性。共价键的本质和特点共价键的本质和特点共价键的本质共价键的本质是由于原子相互接近时轨道重是由于原子相互接近时轨道重叠（即波函数叠加），原子间通过共用自旋叠（即波函数叠加），原子间通过共用自旋相反的电子对使能量降低而成键。相反的电子对使能量降低而成键。离子键与共价键离子键与共价键 共价模型的修正共价模型的修正Electronegativity(EN)is a measure of the electron-pulling power of an atom on an electron pair in a molecule.Compounds composed of elements
23、 with large difference in EN(2)tend to have significant ionic character in their bonding.离子模型的修正离子模型的修正Compounds composed of high polarizing(使极化使极化)cations and highly polarizable(被极化被极化)anions have a significant covalent character in their bonding.3、分子和离子的形状分子和离子的形状(The shapes of molecules and ions)
24、价层电子对互斥理论价层电子对互斥理论 The VSEPR model(Valence-shell electron-pair repulsion)VSEPR(Valence-shell electron-pair repulsion)价层电子对互斥理论价层电子对互斥理论可以定性判断和预见分子的几何构型可以定性判断和预见分子的几何构型 分子的共价键中的分子的共价键中的价电子对价电子对以及以及孤对电子孤对电子由于相互排斥作由于相互排斥作用而趋向尽可能彼此远离，分子尽可能采取对称的结构。用而趋向尽可能彼此远离，分子尽可能采取对称的结构。若一个中心原子和几个配位原子形成分子时，分子的几何若一个中心原子
25、和几个配位原子形成分子时，分子的几何构型取决于中心原子周围地价电子数目。价电子包括价层构型取决于中心原子周围地价电子数目。价电子包括价层轨道中轨道中成键电子对成键电子对(bp)和孤电子对和孤电子对(lp).不同价电子对间排斥作用的顺序为：不同价电子对间排斥作用的顺序为：lplp lpbp bpbp 分子中的多重键按单键处理（分子中的多重键按单键处理（忽略忽略 键！键！）。）。价层电子对数确定方法：价层电子对数确定方法：价层电子对数价层电子对数 (中心原子价电子总数中心原子价电子总数配位原子提供电子数配位原子提供电子数 离子电荷数离子电荷数)配位原子提供电子数：配位原子提供电子数：H,Cl,1;
26、O,S,0;N,-1.VSEPR(Valence-shell electron-pair repulsion)According to the VSEPR model,bonding pairs and lone pairs,to reduce repulsions,take up positions around an atom that maximize their separations.The shape of the molecule is determined by the locations of the atoms attached to the central atom.El
27、ectron pairs in multiple bonds are treated as a single unit equivalent to one region of high electron concentration.Lone pairs on the central atom contribute to the shape of the molecule but are ignored when we name the shape.The molecule adjusts its shape to reduce lone pair-lone pair and lone pair
28、-bonding pair repulsions.Rules of VSEPR Theory 1)Draw the best Lewis dot structure of the molecule 2)Assign a steric number(SN)to the structure SN=(#of bonded atoms)+(#of lone pairs)3)Place the atoms and lone pairs as far apart as possible(while still keeping them connected to the central atom)4)Ded
29、uce the molecular geometry by ignoring the positions of the lone pairs 5)Remember,lone pairs are FAT价价电电子子对对数数目目与与分分子子构构型型电子对数目：电子对数目：2，3，4电子对数目：电子对数目：5，6价层电子对数价层电子对数=（中心原子价电子数（中心原子价电子数+配位原子提供电子数配位原子提供电子数 离子电荷数代数值）离子电荷数代数值）=键数键数+孤电子对数孤电子对数配位原子配位原子提供电子数：提供电子数：氢和卤素原子：各提供氢和卤素原子：各提供1个电子个电子(形成一个形成一个 键键)；
30、氧和硫原子：提供氧和硫原子：提供0个电子个电子(中心原子提供中心原子提供2个电子形个电子形成一个成一个 键键)；氮原子：提供氮原子：提供-1个电子个电子(中心原子提供中心原子提供3个电子形个电子形成一个成一个 键键)；Methane(CH4)Lewis structure:Central atom carbon Valence electrons on central atom 4 4 H each contribute 1 electron:4 Total 8 Divide by 2 to give electron pairs 4 4 electron pairs:tetrahedral
31、for the four shape-determining electron pairs 甲烷甲烷分子构型：正四面体分子构型：正四面体Ammonia,NH3 Lewis structure:Central atom nitrogen Valence electrons on central atom 5 3 H each contribute 1 electron:3 Total 8 Divide by 2 to give electron pairs 4 4 electron pairs:tetrahedral geometry for the four shape-determining
32、 electron pairs The H-N-H bond angles are slightly less(106.6)than the ideal tetrahedral angle of 109.5.氨氨分子构型：角锥型分子构型：角锥型电子构型与电子构型与分子构型分子构型不一致不一致Water,OH2 Lewis structure:Central atom oxygen Valence electrons on central atom 6 2 H each contribute 1 electron:2 Total 8 Divide by 2 to give electron pa
33、irs 4 4 electron pairs:tetrahedral for the four shape-determining electron pairs 水水分子构型：角型分子构型：角型电子构型与电子构型与分子构型分子构型不一致不一致Boron trifluoride,BF3 Lewis structure:Central atom boron Valence electrons on central atom 3 3 F each contribute 1 electron:3 Total 6 Divide by 2 to give electron pairs 3 3 electr
34、on pairs:trigonal geometry for the three shape-determining electron pairs BF3分子构型：平面三角分子构型：平面三角hexafluorophosphate,PF6-Lewis structure:Central atom phosphorus Valence electrons on central atom 5 6 F each contribute 1 electron:6 Add one for the negative charge on P 1 Total 12 Divide by 2 to give elec
35、tron pairs 6 6 electron pairs:octahedral geometry for the six shape-determining electron pairs PF6-分子构型：正八面体分子构型：正八面体Chlorine trifluoride,ClF3 Lewis structure:Central atom chlorine Valence electrons on central atom 7 3 F atoms each contribute 1 electron:3 Total 10 Divide by 2 to give electron pairs
36、5 5 electron pairs:trigonal bipyramidal geometry for the five shape-determining electron pairs ClF3分子构型：分子构型：T字型字型电子构型与电子构型与分子构型分子构型不一致不一致电子数为电子数为5时，孤对总是尽先处时，孤对总是尽先处于三角双锥的腰部位置于三角双锥的腰部位置Isomers The case of ClF3 is interesting.The calculation shows that the shape is based upon five electron pairs and
37、the favoured geometry is therefore trigonal bipyramidal.There are three bonded groups and so two lone pairs.This is indeed the case,but the point of interest here is the location of the lone pairs.There are three possible ways of placing two electron pairs in a trigonal bipyramidal geometry.These th
38、ree structures have respectively zero,one,and two lone pairs in the axial sites.For the VSEPR method to be worth much,it has to successfully predict the correct geometry.To approach this problem it is necessary to know the relative magnitude of the various kinds of electron pair-electron pair intera
39、ctions.There are three possible interactions:三种构型三种构型 选择选择lplp lpbp bpbpVSEPR calculation for perchlorate,ClO4-Perchlorate,ClO4-Lewis structure:Central atom chlorine Valence electrons on central atom 7 4 terminal oxygens each contribute 1 electron in the four bonds 4 Add one for the negative charge
40、located on Cl 1 Subtract four for the four electrons contributed by Cl to the four bonds(one for each):-4(双键因素）双键因素）Total 8 Divide by 4 to give electron pairs 4 4 electron pairs:tetrahedral geometry for the four shape-determining electron pairs ClO4分子构型：正四面体分子构型：正四面体含氧原子的情况：净结果含氧原子的情况：净结果是是O原子不提供价电子
41、。原子不提供价电子。Nitrogen dioxide,NO2 Lewis structure:Central atom nitrogen Valence electrons on central atom 5 2 terminal oxygens each contribute 1 electron in the two s bonds:2 Subtract two for the two electrons contributed by N to the two pi bonds:-2(双键因素）双键因素）Total 5 Divide by 2 to give electron pairs
42、2.5 33 electron pairs:trigonal geometry for the 3 shape-determining s-framework orbitals NO2分子构型：角型分子构型：角型含氧原子的情况：净结果含氧原子的情况：净结果是是O原子不提供价电子。原子不提供价电子。电子构型与电子构型与分子构型分子构型不一致不一致适用性与局限性适用性与局限性价层电子对互斥理论价层电子对互斥理论 Predicts the shapes of molecules Works very well for octets and for“expandedoctets”(2nd and 3r
43、d row elements)Doesnt work at all for transition metalcomplexes-too many groups and electronsto allow the use of sterics alone不能说明成键原理和键的相对稳定性不能说明成键原理和键的相对稳定性Ronald J.GillespieDepartment of Chemistry,McMaster Uni6ersity,1280 Main Street West,Hamilton,Ont.,CanadaCoordination Chemistry Reviews,197(200
44、0),3-19;5169.4、杂化轨道、杂化轨道(Hybrid Obital)实验测得实验测得 CCl4、CH4等的立体构型为正四面体等的立体构型为正四面体（tetrahedral）在同一个原子中在同一个原子中能量相近能量相近的不同类型（的不同类型（s,p,d,）的几个原子轨道波函数可以相互叠加而组成的几个原子轨道波函数可以相互叠加而组成同等数目同等数目的的能量完全相同能量完全相同的的杂化轨道杂化轨道。sp杂化轨道杂化轨道:BeF2 的立体结构为线性的立体结构为线性激激发发杂杂化化sp2杂化杂化sp杂化杂化sp2杂化：杂化：乙烯乙烯sp3杂化：杂化：sp3杂化及其成键过程杂化及其成键过程杂化轨
45、道与分子形状杂化轨道与分子形状(Hybridization and molecular shape)ElectronarrangementNumber of atomic orbitalsHybridization of the central atomNumber of bybrid orbitalsLinear线形线形2sp2Trigonal planar三角平面三角平面3sp23Tetrahedral四面体四面体4sp34trigonal bipyramidal三角双锥三角双锥5sp3d5Octaheral八面体八面体6sp3d26分子不是因为它有分子不是因为它有sp3杂化轨道而具有四面
46、体形状！杂化仅杂化轨道而具有四面体形状！杂化仅仅是描述给定分子结构中成键的一种理论方式。仅是描述给定分子结构中成键的一种理论方式。它只是对它只是对分子形状的一个解释分子形状的一个解释，形状本身并非杂化的结果！，形状本身并非杂化的结果！杂化轨道理论不能预测分子的几何构杂化轨道理论不能预测分子的几何构型型立体三角锥立体三角锥共振体共振体（Resonance）和（离域）和（离域 键）键）实验测得：苯中实验测得：苯中CC的键长均相等，为的键长均相等，为139pm.介于介于CC 键长（键长（133pm)和和 CC键长（键长（154pm）之间。）之间。例例 NO3-SO2 NO2 等等 (参见参见p163
47、-164)离域离域 键键(delocalized)但价键理论不能说明但价键理论不能说明氧分子的顺磁性氧分子的顺磁性等。等。顺磁性：顺磁性：要求分子内必须有未成对电子。要求分子内必须有未成对电子。OO？5、分子轨道理论、分子轨道理论(Molecular orbital theory)分子轨道理论是把分子轨道理论是把分子看作一个整体分子看作一个整体，分子轨道，分子轨道可近似地用原子轨道波函数线性组合得到。可近似地用原子轨道波函数线性组合得到。分子轨道分子轨道的数目的数目等于组成分子的各原子的等于组成分子的各原子的原子轨道数目之和原子轨道数目之和。2 个原子轨道可以组合成个原子轨道可以组合成 2个分
48、子轨道，其中一个个分子轨道，其中一个为为成键轨道成键轨道（bonding)，其能量较原来的原子轨道能，其能量较原来的原子轨道能量降低，用量降低，用 或或 表示；另一个为表示；另一个为反键轨道反键轨道(antibonding)，其能量较原来的原子轨道能量升高，其能量较原来的原子轨道能量升高，用用 *或或 *表示表示.电子在分子轨道上的排布也遵从原子轨道电子排电子在分子轨道上的排布也遵从原子轨道电子排布的同样原则。布的同样原则。分子轨道理论分子轨道理论(Molecular orbital theory)The molecular orbital theory considers the set o
49、f orbitals involved in bonding(the molecular orbitals or MOs)to be an attribute of the molecule rather than of the individual atoms.Atomic orbitals overlap to form molecular orbitals.When two atomic orbitals of equal energy overlap,they produce two molecular orbitals.One of the molecular orbitals pr
50、oduced is lower in energy than the original atomic orbitals.This is the bonding MO,designated.The bonding MO concentrates electron density between the nuclei,drawing them closer by electrostatic attraction.The other MO formed is higher in energy than the original atomic orbitals and has very little
