chapter5-ChemicalPeriodicity(化学周期性)PPT格式课件下载.ppt

1、5Chemical Periodicity化学周期性The reaction of H2O and Li（left）to produce LiOH and H2（g）is much slower than the analogous reaction between H2O and Na（right）.Chapter Goals5-1 More About the Periodic TablePeriodic Properties of the Elements 元素的周期特质5-2 Atomic Radii 原子半径5-3 Ionization Energy游离能5-4 Electron A

2、ffinity电子亲和力5-5 Ionic Radii 离子半径5-6 Electronegativity 电负性5-7 Oxidation StatesChemical Reactions and Periodicity5-7 Hydrogen&#the HydridesHydrogenReactions of Hydrogen and the Hydrides5-8 Oxygen&#the OxidesOxygen and OzoneReactions of Oxygen and the OxidesCombustion ReactionsCombustion of Fossil Fuel

3、s and Air Pollution2More About the Periodic TableEstablish a classification scheme of the elements based on their electron configurations.Noble Gases 钝气 Group 8AAll of them have completely filled electron shells.Since they have similar electronic structures,their chemical reactions are similar.nsns2

4、npnp6He 1s2Ne He 2s2 2p6Ar Ne 3s2 3p6Kr Ar 4s2 3d10 4p6Xe Kr 5s2 4d10 5p6Rn Xe 6s2 4f14 5d10 6p63More About the Periodic TableRepresentative Elements典型元素Are the elements in A groups on periodic chart.These elements will have their“last”electron in an outer s or p orbital.These elements have fairly r

5、egular variations in their properties.4More About the Periodic Tabled-Transition Elements过渡金属元素Elements on periodic chart in B groups.Sometimes called transition metals.Each metal has d electrons.ns（n-1）d configurationsThese elements make the transition from metals to nonmetals.Exhibit smaller varia

6、tions from row-to-row than the representative elements.5First transition series（4s and 3d orbital occupy）:#21Sc through 30ZnSecond transition series（5s and 4d orbital occupy）:#39Sc through 48CdThird transition series（6s and 5d orbital occupy）:#52La and 72Hf to 80HgFourth transition series（6s and 5d

7、orbital occupy）:#89Ac and 104Rf to 112More About the Periodic Tablef-transition metals Sometimes called inner transition metals.Electrons are being added to f orbitals.6Outermost electrons have the greatest influence on the chemical properties of elements.Adding an electron to an s or p orbital dram

8、atic change in the physical and chemical propertiesAdding an electron to a d or f orbital much smaller effect on propertiesPeriodic Propertiesof the ElementsAtomic Radii 原子半径Ionization Energy游离能Electron Affinity电子亲和力Ionic Radii 离子半径Electronegativity 电负性78Atomic Radii原子半径relative sizesAtomic radii in

9、creaseAtomic radii decrease Atomic radii decrease =10-10m同周期典型元素大致随原子序增加 原子半径愈小同族元素原子序增加 原子半径愈大Atomic RadiiThe reason the atomic radii decrease across a period is due to shielding or screening effect屏蔽效应.Effective nuclear charge有效核电荷,Zeff,experienced by an electron is less than the actual nuclear ch

10、arge,Z.最外层电子受原子的吸引力被内层电子对外层电子的排斥力给抵销即称屏蔽效应Moving across a period,each element has an increased nuclear charge and the electrons are going into the same shell（2s and 2p or 3s and 3p,etc.）.Consequently,the outer electrons feel a stronger effective nuclear charge.For Li,Zeff +1For Be,Zeff +29有效核电荷镁的有效核

11、电荷约为12 10=2原子核质子数内层电子数总和原子半径随原子序数的增加呈现周期性变化。#这与原子有效核电荷的周期性变化相关因为有效核电荷愈大,对外层电子的吸引力愈大,原子半径就愈小各周期的主族从左到右,电子层数不变,有效核电荷增加明显,原子半径的逐渐减少也就比较明显长周期中的过渡元素原子半径先是缓慢缩小然后略有增大内过渡元素，有效核电荷变化不大，原子半径几乎不变稀有气体原子半径突然增大，因为它是van der Waals半径 同一主族从上到下，由于电子层数增加，使遮罩效应明显加大，所以原子半径递增。#11凡得瓦半径 为两个相邻非键结原子间距离的一半Atomic RadiiExample 5-

12、1:#Arrange these elements based on their atomic radii.Se,S,O,TeP,Cl,S,SiGa,F,S,AsCs,F,K,Cl6AO S Se TePeriod 3Cl S P SiF S As GaF Cl K IE1 It always takes more energy to remove a second electron from an ion than from a neutral atom.2.IE1 generally increases moving from IA elements to VIIIA elements.I

13、mportant exceptions at Be&#Mg,N&#P,etc.due to filled and half-filled subshells.3.IE1 generally decreases moving down a family.IE1 for Li IE1 for Na,etc.15DecreaseDecreaseincrease increase 随原子序增大渐增趋势随原子序增大而递减同一族元素的游离能随原子序的增加而变小例如第1族元素的第一游离能大小顺序为：#Li Na K Rb Cs Fr同族元素的原子序愈大，原子半径愈大，最外壳层电子受原子核的引力愈小，故电子愈

14、容易移除。#游离能的周期性 同一周期之各元素的第一游离能，随原子序的增加，呈现锯齿状的增加原子半径愈小，且有效核电荷愈大，所需的IE愈大 同一周期第一游离2族 3族，镁（738 kJ/mol）铝（578 kJ/mol）15（5A）16（6A），磷（1012 kJ/mol）硫（1000 kJ/mol）同一周期过渡元素，因原子半径及有效核电荷彼此差异不大，故其第一游离能彼此差异相对较小 游离能的规则 同一周期元素的第一游离能从左至右渐增,但在中间有些起伏IIA IIIA,而VA VIA:#IIA（ns2）IIIA（ns2np1）是因为np能阶较ns高,因此IIIA原子的游离能较小VA（ns2np3

15、）VIA（ns2np4）因为VA 族的价电子组态为全半填满,而VIA族有一个p轨域填入两个电子,将增加电子的斥力,因此较易移去,故VA VIA19First Ionization Energies of Some Elements20Elements with low ionization energies（IE）easily lose to form cations（positive charge）Ionization EnergyExample 5-2:#Arrange these elements based on their first ionization energies.Sr,B

16、e,Ca,MgAl,Cl,Na,PB,O,Be,NNa,Mg,Al,SiSr Ca Mg BeNa Al P ClB Be O NNa Al Mg 0 energy is absorbedIf electron affinity 0 energy is released 对于放热愈多放热愈多的反应，我们称其电子亲和力愈大电子亲和力愈大，表示该原子愈易获得电子Electron affinity is a measure of an atoms ability to form negative ions Symbolically:#25atom（g）+e-+EA ion-（g）Electron Affinity26Mg（g）+e-+231 kJ/mol Mg-（g）EA=+231 kJ/molBr（g）+e-Br-（g）+323 kJ/molEA=-323 kJ/molTwo examples of electron affinity values:#Most elements have no affinity for an additional electron and thus have an electron aff