山大《医学基础化学》双语课件07Atomic Structure

1、 Chapter Seven Atomic Structure neutrons atoms protons (positive charge ) electrons (negative charge)7-1 Changing Ideas about Atomic Structure7-2 The Quantum Mechanical Description of Electron in Hydrogen Atoms 7-3 Electron Configuration of Many- electron Atoms7-4 The Periodic Table and Periodic Law

2、 1805 dolton proposed atom theory, proved exist of atom1900 electron were discovered1911 Ruthrford proposed the atomic nucleus by -ray scatting1931 neutron were discovered7-1.1 The Bohr theory of Hydrogen AtomRuthrfords nuclear modelFigure 7-1: In classical theory: 1.atoms constructed are not stable

3、; 2.the electron would quickly spiral into the nucleus.3. Not is the line spectra of atomsContinuous spectrumNa Atomic Line Spectra（H、He、Li、Na、Ba、Hg、Ne light emission)In 1913, Niels Bohr(1885-1962), founded Bohr theory by using the work of Planck and EinsteinQuantum of concept emission Atom a copy o

4、f energy absordquantumno continuumLeast unit Physicist Albert Einstein (1879 -1955)The Photoelectric EffectEinstein used the quantum theory to explain the photoelectric effect :Each energy packet called photon, is a quantum of energy E=h v h Plancks constant = 6.62310-34J s. E = hv =Photons of high

5、frequency radiation have high energies, whereas photons of lower frequency radiation have lower energy.（波粒二象性）7-1.1 The Bohr theory of Hydrogen Atom Bohr set down the following two postulates to account for: (1) the stability of the hydrogen atom (that the atom exists and its electron does not conti

6、nuously radiate energy and spiral into the nucleus) (2) the line spectrum of the atom. Bohr theory of Hydrogen Atom Bohr assumed that: 1.Energy-level postulate an atom looked something like the solar system: 1) a nucleus at the center 2) the electron could have only certain orbits L 代表电子运动轨道的角动量（L=

7、p r =mv r ）P 是电子轨道运动动量，r 是轨道半径，m 是电子的质量，v 是电子的运动速度。 量子化条件：电子在任意轨道做圆周运动的角动量mv r必须是 的整数倍， n = 1, 2, 3, +n=1n=2n=3 r =52.9pm3) energy levels: an electron in an atom can have only specific energy values, which are called the energy levels of the electron in the atom En = - (Z2/n2) 2.180 10-18J (for H at

8、om) Z : 核电荷数 n : 能级数 1, 2, 3, - Bohr theory of Hydrogen Atomn值越大，表示电子运动轨道离核越远，能量越高。2. Transitions（跃迁）between energy levels photons are given off or absorbed when an electron moves from one orbit to another. ground state a lower energy state ( if n = 1, is called ground state )excited state a high en

9、ergy state( if n = 2、3, is called ground state) Ground stateExcited stateEnergy of emitted photon E = Ei - Ef = hvEi a higher energy level (initial energy level) Ef a lower energy level (final energy level ) In 1885, J.J. Balmer showed that the wavelengths, , in the visible spectrum of hydrogen coul

10、d be reproduced by a simple formula. 1 1 1 - = 1.097 107m-1 ( - - -) 2 2 n 2postulate from level n = 4 to level n = 2 light of wavelength 486 nm (blue green ) is emittedHydrogen atom spectraVisible lines in H atom spectrum are called the BALMER series. High EShort lHigh nLow ELong lLow nEnergyUltra

11、VioletLymanInfraredPaschenVisibleBalmer653214n Bohrs theorySuccessful1.established the concept of atomic energy levels (atomic orbit)2. explaining the spectrum of hydrogen Unsuccessful 1. atomic orbit is fastness 2. cant explain minuteness the spectrum of hydrogen atomLouis-Victor de Broglie, (1892

12、-1987, France)In 1929, he was awarded the Nobel Prize for Physics for his research on quantum theory and his discovery of the wave nature of electrons. He showed that the wavelength of moving particles is equal to Plancks constant divided by the momentum. 7-1.2 De Broglie Waves (Matter Waves)Mass: h

13、 , Particle: wave properties ignoredh， wave properties can not ignoredis short（7-4）例71 分别计算m=2.510-2kg，v = 300ms-1的子弹 和me=9.110-31kg v =1.5106 ms-1的电子的 波长，并加以比较。解： 按（7-4）式，子弹的波长为： 电子的波长为：计算结果表明，子弹的波长很短，完全可以不予考虑。1927年美国物理学家Davisson C和Germer L根据电子的波长 与X射线波长相近，用电子束代替X射线，用镍晶体薄层 作为光栅进行衍射实验，得到与X射线衍射类似的图像，

14、 证实了电子的波动性。电子的波粒二象性（Davisson和Germer实验 ） X-diffractedelectron diffracted7-1.3 The Heisenberg Uncertainty principle 1927 ,He recognized : no experimental method can be devised that will measure simultaneously the precise position(x) as well us the momentum (mv) of an object. Heisenberg German physicis

15、t (1901-1971)Uncertainty principle formula p uncertainty of the momentum x uncertainty of the position h Plancks constantThe more precisely one knows p, the less precisely x is known, and vice versa.ExampleSuppose x=1.0 10- 4 m for a substance with mass of 0.01kg In hydrogen atom, for an electron, v

16、 =106m/s , suppose x=1.0 10- 10 m,电子速度的不准确量与其速度本身十分接近 (中文p148_)Quantum or Wave MechanicsSchrodinger applied idea of e- behaving as a wave to the problem of electrons in atoms.E. Schrodinger1887-1961 1933 received the Nobel Prize E the total energy V the potential energy m a particle in terms of its

17、massx y z respect to its position in three dimensions7-1.4 Schrdinger Equation (wave function) Solution to WAVE EQUATION gives set of mathematical expressions called WAVE FUNCTIONS (psi)wave function has an amplitude（振幅） at each position in space (just as for a water wave or a classical electromagne

18、tic wave). is a function of distance and two angles. (r,)、 does NOT describe the exact location of the electron.For 1 electron, corresponds to an ORBITAL the region of space within which an electron is found.7-2.1 Wave Function, Atomic Orbital and Electron Cloud7-2.2 Atomic Orbital _ Quantum Numbers

19、 n the principal quantum number l the angular momentum quantum number m the magnetic quantum number. they will be used to describe atomic orbitals and to label electrons that reside in them. 1. Principal quantum number (n): Shell K L M N . . . n 1 2 3 4 . . .As n increases, the orbitals extend farth

20、er from the nucleus,average position of an electron in these orbitals is farther from the nucleusEnergies: KLMNO 12 3 4 5 2. Angular momentum quantum number (l ) Within each shell of quantum number n , there are n different kinds of orbital, each with a distinctive shape, denoted by the l quantum nu

21、mber. subshell s p d f g . . . l 0 1 2 3 4 . . .(n-l) Energies: sp d f g3. Magnetic quantum number (m): A subshell has the same shape, but a different orientation, or direction, in space. m = (2 l + 1) or Each orbital of a particular subshell (no matter how it is oriented in space) has the same ener

22、gy. Example: p orbit have 3 different orientation p x. p y p z About Quantum Numbers OrbitalAn atomic orbital is defined by 3 quantum numbers:Electrons are arranged in shells and subshells of RBITALS . n shell l subshell m designates an orbital within a subshelln l m Table 7-1: The allowed sets of q

23、uantum numbers for atomic orbitals 4. Spin quantum number (ms) : ms the spin quantum number refers to a magnetic property of electrons called spin. Values for the spin quantum number are +1/2 and 1/2. A fourth quantum number Note: n. l. m. msthey will be used to describe electrons that reside in the

24、mQUANTUMNUMBERS1. Which of the following is not a valid set(有效的组合) of four quantum numbers to describe an electron in an atom? (1) 1, 0, 0, + (2) 2, 1, 1, + (3) 2, 0, 0, (4) 1, 1, 0, +2. The energy of an orbital in a many-electron atom depends on (1) the value of n only (2) the value of l only (3) t

25、he values of n and l (4) the values of n, l, and mRadial wave functionangular wave function7-2.3 Sizes and Shapes of Atomic OrbitalsSpherical coordinates x = r sin cos y = r sin sin z = r cosShapes of the orbitalsShapes of the orbitals for: (a) an s subshell(b) a p subsell(c) a d subshell ?如：氢原子的角度部

26、分【s轨道】Ys是一常数与(q,f)无关，半径为:【pz轨道】节面：当cosq = 0时，=0，q = 90我们下来试做一下函数在Pz平面的图形。3060090+3060节面：当 = 90 cos= 0 =0时波函数的角度分布图由图可知，原子轨道的角度分布图有正负之分，这对于讨论分子的化学键及对称性十分重要。同样地，可以画出其它原子轨道的角度分布图。The Probability Function (2) Electron Cloud 2 is related to the probability per unit volume such that the product of 2 and a

27、 small volume (called a volume element) yields the probability of finding the electron within that volume. 1. Electron Cloud The total probability of locating the electron in a given volume (for example, around the nucleus of an atom) is then given by the sum of all the products of 2 and the corresp

28、onding volume elements.2px2pzf orbitals|n,l,m(r,) |2 = R2n,l(r) Y2l,m(,) Probability density电子云的径向分布图 P=|2 dV Probability 几率(dP)=几率密度(|2)体积(dV)电子云的径向分布图考虑离核距离为r，厚度为dr的薄层球壳内发现电子的几率. 1s球壳微体积： dV = 4r2drD(r) =4r2dr R2(r)-壳层几率（球壳层内发现电子的几率）P=|2 dV= |2 4r2dr =4r2dr R2(r) Y2l,m(,)Probability = D(r) Y2l,m(,

29、)Radial distribution function diagramAngular distribution function diagram离核越近： r值越小，体积越小，|2越大，D(r)不是最大，离核越远： r值越大，体积越大，|2越小，D(r)亦不是最大，在ao处： |2不是最大的, 但体积较大，使D(r)可达最大。P= |2 4r2dr ao=52.9pm处。当r=2ao时， D(r)=0,出现第一个节面。当r=4ao时， D(r)又出现最大值,此即2s电子云当r=2ao时， D(r)=0,出现第一个节面。当r=4ao时， D(r)又出现最大值,此即2s电子云电子云的径向分布图

30、峰数 n-l 7-3 Electron Configuration of Many-electron Atoms 1. An electron configuration describes the arrangement of electrons in the subshells of an atom. 2. The chemical properties of elements are related to these configurations. 3. The four quantum numbers n, l, m, and ms enable us to label complet

31、ely an electron in any orbital in any atom. Order of filling orbitals Generally, the energy of an orbital depends on the quantum n and l . E1s E2sE 2p E3sE3p E3d E4sE 4p E 4d E4f E5s1s 2s2p 3s3p 4s3d4p 5s4d5p 6s4f5d6p 7s Why? This phenomenon can be explained by shielding effect (screening effect) an

32、d penetrating effect. The shielding effect is that it reduces the electrostatic attraction between protons in the nucleus and the electron in outside orbital. 2. The penetrating effect of an electron can decrease the energy of orbital.1sD(r)r2s3sD(r)r3d3p3s图1 l 相同， n不同时的比较图2 n 相同， l 不同时的比较 从上图可以看出：

33、（1） l相同，n不同: 1s2s3s . n 增大时，电子离核的距离 （主峰）将增加。 （2） n相同，l不同 3s3p3d. l 值大，峰个数减少。 l 值小，电子在核附近出现的机会（钻穿峰）较多。The penetrating effect钻穿效应: 外层电子向内层穿透，导致内层电子对它的屏蔽作用减弱的效应叫钻穿效应(3) n,l都不同时，将出现能级交错 :4s3d4p 为什么 2s 价电子比 2p 价电子受到较小的屏蔽?Question 2s电子云径向分布曲线除主峰外,还有一个距核更近的小峰. 这暗示, 部分电子云钻至离核更近的空间, 从而部分回避了其他电子的屏蔽.The electr

34、on fill law1.principle of energy levels lowest Electrons in an atom occupy the lowest possible energy levels, or orbitals. 2.The Pauli exclusion principle: No two electrons in the same atom can have the same set of four quantum numbers. 3.Hunds rule: Every orbital in a subshell is singly occupied (f

35、illed) with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin; All of the electrons in an atom reside in the lowest energy orbitals possible as long as permission of Pauli exclusion principle .The electrons filling order is： 1s,

36、2s2p, 3s3p, 4s3d4p, 5s4d5p, 6s4f5d6p, 7s5f 1.principle of energy levels lowest1s2s2p3s3p4s4p3d5s5p4d6s6p5d4f2. Pauli Exclusion Principle (2n2)The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers: n l m and ms. Thus, for two electrons to

37、occupy the same orbital, one must have ms = + and the other must have ms = . electrons with the same spin keep as far apart as possible electrons of opposite spin may occupy the same orbital3. Hunds rule(洪特规则)This rule states that for orbitals with the same energy, the lowest energy is attained when

38、 the number of electrons with the same spin is maximized.Example Boron(atomic number =5) B 1s22s2 2p1 Nitrogen (atomic number =7) N 1s22s2 2p3 Magnesium (atomic number =12) Mg 1s22s2 2p63s2 or Ne3s2 Chromium (atomic number =24) Copper (atomic number =29) ? Lanthanum (atomic number =57) According to

39、Hunds rule and Pauli exclusion principle, we can writing the electron configurations for other elements. Example: chromium (Z = 24) Ar4s13d 5 or Ar4s23d4 half-filled (s1 p3 d5)Subshells completely empty(s0p0d0) stability completely filled (s2 p6 d10) 电子层结构式要与原子的电子排布式区别开，以29号元素铜为例：电 子 排 布 式： 29Cu: 1s

40、2 2s2 2p6 3s2 3p6 4s1 3d10 电子层结构式： 29Cu: 1s2 2s2 2p6 3s2 3p6 3d10 4s1（或电子构型式) 7- 4 The Periodic Table and Periodic Law Then in 1869, Russian chemist Dimitri Mendeleev (1834-1907) proposed arranging elements by atomic weights and properties (Lothar Meyer independently reached similar conclusion but p

41、ublished results after Mendeleev). Mendeleevs periodic table of 1869 contained 17 columns with two partial periods of seven elements each (Li-F & Na-Cl) followed by two nearly complete periods (K-Br & Rb-I). 7- 4 The Periodic Table and Periodic Law The modem Periodic Table consists of 7 horizontal(水

42、平) rows of elements (often referred to as periods or series) and 32 vertical（垂直） columns of elements (referred to as families or groups). 维尔纳长式周期表periodsshort periodFirst (2 element)secondthirdlong periods(8 element)(8 element)fourthfifth18 elements18 elementssixth32 elementsseventh32 elementsperiod

43、s or seriesThe first short period contains two elements hydrogen (H)and helium（He). The second short period contains eight elements, beginning with lithium (Li) and ending with neon (Ne).The third short period also contains eight elements, beginning with sodium (Na)and ending with argon (Ar). The tw

44、o long periods, The fourth period and the fifth period are two long periods, each of which contains 18 elements. The fourth period includes the elements from potassium (K)through krypton (kr). Within this period are the elements from scandium (Sc)through copper(Cu), which are known as the first tran

45、sition series. The fifth period is begins with rubidium (Rb)and ends with xenon (Xe). Within this period are the elements yttrium (Y) through silver (Ag),which comprise the second transition series.The sixth periodThe sixth period, beginning with cesium (Cs)and ending with radon (Rn),contains 32 ele

46、ments. The third transition series, made up of lanthanum (La)and the elements hafnium (Hf)through gold (Au) The sixth periodThe third transition series is split: between lanthanum and hafnium is a series of 14 elements, cerium (Ce) through lutetium (Lu),called the first inner transition series, or t

47、he lanthanide series or the rare earth elements. The seventh period The seventh period extends from francium through element number 118. However, no elements after element 109 have been characterized. The known elements in this period include a part of the fourth transition series (actinium, and ele

48、ments 104 through 109). Electronic Structure and the Periodic Law the periodicity with respect to the number of valence electrons; valence electrons that is, electrons in the outermost shell.the Periodic Table is simply an arrangement of atoms that puts elements with the same number of valence elect

49、rons in the same group. 表：基态电中性原子的电子组态1 氢H 1s12 氦He 1s23 锂Li He 2s14 铍Be He 2s25硼B He 2s22p16 碳C He 2s22p27 氮N He 2s22p38 氧O He 2s22p49 氟F He 2s22p510氖Ne 1s2 2s22p611钠Na Ne 3s112镁Mg Ne 3s213铝Al Ne 3s23p114硅Si Ne 3s23p2 15磷P Ne 3s23p3 16硫S Ne 3s23p4 17氯Cl Ne 3s23p5 18氩Ar 1s22s22p63s23p6 19钾K Ar 4s120

50、钙Ca Ar 4s221钪Sc Ar 3d14s222钛Ti Ar 3d24s223钒V Ar 3d34s224铬Cr* Ar 3d54s125锰Mn Ar 3d54s226铁Fe Ar 3d64s227钴Co Ar 3d74s228镍Ni Ar 3d84s2不符合构造原理 价层电子 价电子层 “电子仁”或“电子实”1-48号元素的核外电子层结构1H1s117ClNe3s23p533AsAr3d104s24p32He1s218ArNe3s23p634SeAr3d104s24p43LiHe2s119KAr4s135BrAr3d104s24p54BeHe2s220CaAr4s236KrAr3d10

51、4s24p65 BHe2s22p121ScAr3d14s237RbKr5s16CHe2s22p222TiAr3d24s238SrKr5s27NHe2s22p323VAr3d34s239YKr4d15s28OHe2s22p424CrAr3d54s140ZrKr4d25s29FHe2s22p525MnAr3d54s241NbKr4d45s110NeHe2s22p626FeAr3d64s242MoKr4d55s111NaNe3s127CoAr3d74s243TcKr4d55s212MgNe3s228NiAr3d84s244RuKr4d75s113AlNe3s23p129CuAr3d104s145RhKr4d85s114SiNe3s23p230ZnAr3d104s246PdKr4d1015PNe3s23p331GaAr3d1