无机化学无机化学英文PPT (7).ppt

《无机化学无机化学英文PPT (7).ppt》由会员分享，可在线阅读，更多相关《无机化学无机化学英文PPT (7).ppt（11页珍藏版）》请在得力文库 - 分享文档赚钱的网站上搜索。

1、Definition:In the standard state,the energy absorbed when an ionic crystal is converted into a gaseous positive ion and a gaseous negative ion by the following stoichiometric reaction,expressed as U.U3.lattice energyMaXb(s)aMb+(g)+bXa-(g)(g)Cl+(g)NaNaCl(s)-+Sample：影响晶格能的因素：影响晶格能的因素：离子的电荷离子的电荷(晶体类型相同

2、时晶体类型相同时)离子的半径离子的半径(晶体类型相同时晶体类型相同时)晶体的结构类型晶体的结构类型 离子电子层结构类型离子电子层结构类型Z，U 例：U(NaCl)U(CaO)The factors that affect the lattice energy：Charge of ions(same crystal type)Radius of ions(same crystal type)The type of crystal structure The electron layer structure of ionZ，U such as：U(NaCl)U(CaO)Describes the

3、ability of an ion to deform other ionsThe polarizing force of an ion(f)：The physical quantity that describes the deformabilityThe polarizability of an ion()：3.Ionic polarization unpolarized anionpolarized anionPolarization of ionsDefinition:The phenomenon that ions generate induced dipoles in an ele

4、ctric field(1)Ions are deformable,so they can be polarized by electric fields.(2)Ions as charged particles can act as electric fields to deform other ions.This ability is called polarization.Therefore,ions have duality:polarization ability and self-deformation.1.General law of ionic polarizability()

5、Ionic radius r:The greater r,the greater.Sample：Li+Na+K+Rb+Cs+;F-Cl-Br-(Mg2+)Ionic charge:a large negative charge has a high polarizabilitySample：(S2-)(Cl-)The shell configuration of the ion:(18+2)e-,18e-9-17e-8e-Sample：(Cd2+)(Ca2+);(Cu+)(Na+)r/pm 97 99 96 95 2.General law of ionic polarization forc

6、es(f)Ion radius r:r smaller,larger polarization force.Ionic charge:more charge,larger polarization force.The outer electron configuration of the ion：f：(18+2)e-,18e-9-17e-8e-When the positive and negative ions are mixed together,the polarization force of the positive ions and the polarization rate of

7、 the negative ions should be considered,but the deformability of the positive ions in the 18e configuration(Ag+,Cd2+)should be also considered.3.The result of ion polarization Bond transition(from ionic bond to covalent bond)Such as:AgF AgCl AgBr AgIIonic bondCovalent bondDistance between nuclear is

8、 shortened.Ag+Ir/pm126+216(=342)R0/pm 299Without weak strong When the positive ion with strong polarization ability and the negative ion with strong deformation are close to each other,the polarization phenomenon will occur,and the electron cloud deformation of the negative ion will increase,leading

9、 to the enhanced electron cloud density between the two nuclei,and therefore the decreased percentage of ionic bond and the increased percentage of covalent bond.Finally,the ionic bond transitions to covalent bond.Illustrated scheme of polarization of cations The ionic polarization results in the tr

10、ansition from ionic crystals to molecular crystals,leading to the decreased melting and boiling points,and even the solubility of substances Considering the strength of ionic bond,the melting point of Al2O3 should be higher than that of MgO,but this is not true.This phenomenon is due to that the cov

11、alent component of Al2O3 is larger,and molecular crystal is formed.Crystal type change AgCl AgBr AgIr+/r-0.695 0.63 0.58 theoretical crystal NaCl NaCl NaClactual crystal NaCl NaCl ZnScoordination number 6 6 4 Property changeSolubility:AgCl AgBrAgI NaCl dissolves easily in water,whereas CuCl is difficult.