Chap 6C - Chem 210/ WANG/ Chapter 6C Electron Configuration...

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Unformatted text preview: Chem 210/ WANG/ Chapter 6C Electron Configuration Chapter 6.7 to 6.9 Electronic Structure of Atoms 6.7 Many Electron Atoms 6.8 Electron Configurations 6.8 6.9 Electron Configurations & the Periodic Table David's Whizzy Periodic Table http://www.colorado.edu/physics/2000/applets/a2.html Online practice goal: achieve >90% in Chap 6. goal: homework 5 and Quiz 5 http://www.chem.purdue.edu/ gchelp/aos/index.html Atomic Orbitals Fill in the blanks (a) The 4s orbital has ______________ shape and its size is ___________ than a 3s orbital. It has capacity for ________ electrons. (b) 3p designates ______ dumbbell shaped volumes, each has capacity for ______ electrons. http://wps.prenhall.com/esm_brown_chemistry_8e/51/13242/3390185.cw/index.html EOC (end-of-chapter problems) (end-of6.14, 6.16, 6.36, 6.44, 6.54, 6.64, 6.68, 6.74 (textbook page 253-255) 253- due due date – Wed. Sept. 23rd (c) The shape of 3dz2 is like ____________________________ and it has capacity for ____ electrons. http://science.widener.edu/svb/at_orbital/orbitals.html Energy of Atomic Orbitals for Many - electron Systems Energy of atomic orbitals: OneOne-electron system Energy Energy of orbitals is solely depends on n, n, the principal quantum number Same Same n, same E Larger Larger n, higher E Energy of Atomic Orbitals manymany-electron vs. one-electron systems oneOne - electron system has one type of interaction: • Electron-to-nucleus attraction Electron-toattraction • Energy depends on nuclear attractive force only. nuclear only. ManyMany-electron system has two types of interactions: • Electron-to-nucleus attraction Electron-toattraction • Electron-to-electron repulsion Electron-torepulsion • Energy determined by both forces. both • Electrons in the inner shells act as a “shield” to inner lower lower nuclear attractive force on electrons in the outer shell. outer shell. Higher Energy 3d 4s 3s 2s 1s 3p 2p 4s is lower than 3d, larger lower larger n, lower E! Note: 2p is higher than 2s, 3p is higher than 3s, etc. Same n, different E! different Energy of Atomic Orbitals Screening Screening or Shielding Effect In a many-electron system: many• Electrons in the inner shell shield the outer shield the electrons from nuclear attraction. nuclear – This reduction of nuclear attraction is called the screening or shielding effect screening • The effective nuclear charge (Zeff) on outer electrons is lower than the actual nuclear actual charge (Z): Zeff = Z – S Z = (# protons in nucleus) S = (average # of inner electrons) Page 1 Fall 2009 / UM-SJTU JI Chem 210/ WANG/ Chapter 6C Electron Configuration Inner vs. Outer electrons This outer electron is shielded from nuclear attraction by the electrons in inner shells effective nuclear charge, Zeff = protons – inner electrons WHY 2s has lower energy than 2p in 2s energy 2p in many electron systems: Because s orbitals have higher electron density higher around around the nucleus, resulting in less shielding less effect stronger stronger nuclear attraction. spherical 2s allows Also the spherical distribution of 2s allows more “room” less electron-to-electron repulsion. less electron-torepulsion resulting in lower energy than 2p. lower 2p. Electrons in inner shells http://www.scienceclass.net/8th_Notes/Images_8th_Notes/xrf_1.gif Z (actual nuclear charge) = number of protons WHY 4s has lower energy than 3d in 4s energy 3d many electron systems: 3d occupies a smaller space than 4s, its electrons occupies 4s, its should experience stronger nuclear attraction and therefore have lower energy. However, the electronelectron3d than electron repulsive force is much stronger in 3d than in 4s. This causes 4s to have lower energy than 3d. 4s. 4s lower than 3d “Energy” of an Atomic Orbital Atomic “In many-electron systems” many• Depends on n+l , sum of principal and azimuthal quantum numbers – larger n+l: higher energy n+l: equal larger – With equal n+l : larger n has higher energy Question: List these in order of energy: 3p, 3d or 4s. http://science.marshall.edu/castella/chm448/econfig.pdf Electron Spins: An Experimental An Discovery • Each line in the emission spectrum of line in manymany-electron systems is actually “double lines.” • Uhlenbeck and Goudsmit explained in 1925. – Electrons actually spin around itself. spin – Clockwise or counter-clockwise spins counterhave slightly different energy in many electron systems. –Assigned spin quantum number, ms spin Either of 2 spinning directions: A pair of electrons exist in opposite spin directions opposite (antiparallel) without the magnetic field. In a magnetic field, the pair can exist in either “parallel” or “antiparallel”. Antiparallel Antiparallel has Higher energy Parallel is more stable ms = +½ or -½ Page 2 Fall 2009 / UM-SJTU JI Chem 210/ WANG/ Chapter 6C Electron Configuration Pauli exclusion principle Pauli Pauli exclusion principle No two electrons in the same atom can have the same same set of four quantum numbers. four n, l, ml and ms – “Exclusion” means each set of four numbers four belongs exclusively to one electron. exclusively – This allows up to 2 electrons per orbital; up electrons these electrons shares • The same set of n, l, ml (which defines the n, (which atomic orbital) • But have different ms , which can be either which ms = +½ or -½. No two electrons in the same atom can have the same same set of four quantum numbers. four n, l, ml and ms Order of filling orbitals in manymany-electron systems Three rules govern how electrons occupy atomic orbitals: Question: which orbital is this electron occupying: (n, l, ml ms) =(3, 2, 1, +½ )? Question: An electron is present in 2px. Give the set of 4 quantum numbers corresponding to this electron. (n, l, ml ms) = (?, ?, ?, ?) Apply the “orbital filling rules” in Many-electron systems ManyQuestion: Determine the order of fill for: 6s and 5d and 4f. Show work! 1. Lowest energy shell first 2. 2e maximum per orbital. 3. For obitals of the same energy (called degenerate degenerate orbitals, such as 2px, 2py and 2pz): 1 electron in each orbital electron before double-up*! double*This is Hund’s rule. Electrons repel each Hund’s other; they “spread out” among the degenerate orbitals as much as possible. ShortShort-cut to Orbital Filling Order 7s 7p 7d 7f 7g 6s 6p 6d 6f 6g 5s 5p 5d 5f 5g 4s 4p 4d 4f 3s 3p 3d Electron Configuration of Ar (18e) Ar 2s 1s 2p Electron Configuration of K (19e) (19e) Full Full and Condensed Electron Configuration of Sc (21e) Sc Full and Condensed Then go up one line at a time… go Start here… lowest energy first Page 3 Fall 2009 / UM-SJTU JI Chem 210/ WANG/ Chapter 6C Electron Configuration Orbital occupancy for the first 10 elements, H through Ne. Condensed ground-state electron configurations in the first three periods. Order for filling energy sublevels Two ways to illustrate Orbital Occupancies: 1. electron configuration nl # of electrons in the sublevel no colorempty A vertical orbital diagram for the Li ground state light half-filled as s,p,d,f 2. orbital diagram (box or circle) dark - filled, spin-paired Orbital diagrams: show unpaired electrons. Electron Electron Configuration: show orbital filling. The last electron added to an element corresponds to the element’s position in the Periodic table. position Periodic s p H He d Li Be B K Ca Sc Ti Rb Sr Y V N O F Al Na Mg C Si P S Cl Ar Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te Cs Ba La Hf Ne Ta W Re Os Ir I Xe Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac f Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Page 4 Fall 2009 / UM-SJTU JI Chem 210/ WANG/ Chapter 6C Electron Configuration Modified chart for finding electron electron configuration The relation between orbital filling and the periodic table s 1 H He 2 Li Be 3 Na Mg 4 K Ca 3 5 Rb Sr 4 6 Cs Ba 5 7 Fr 6 Ac Ra p 2 d B C N O F Ne 3 Al Si P S Cl Ar Ti V Cr Mn Fe Co Ni Cu Zn 4 Ga Ge As Se Br Kr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd 5 In Sn Sb Te I Xe La Hf Ta W Re Os Ir Pt Au Hg 6 Tl Pb Bi Po At Rn Sc 4 f5 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr The electron configuration for: H= 1s1 s 1 H Li Be 3 B= He 2 Na Mg The electron configuration for Rb: Li= 1s22s1 s 1s22s22p1 Al= 1s22s22p63s23p1 d p 2 B C N O F Ne 3 Al Si P S Cl Ar 4 K Ca 3 Sc Ti V Cr Mn Fe Co Ni Cu Zn 4 Ga Ge As Se Br Kr 5 Rb Sr 4 Y Zr Nb Mo Tc Ru Rh Pd Ag Cd 5 In Sn Sb Te I Xe 6 Cs Ba 5 La Hf Ta W Re Os Ir Pt Au Hg 6 Tl Pb Bi Po At Rn 7 Fr 6 Ac Ra 4 f5 H He 2 Li Be 3 Na Mg 4 K 2 Li Na Mg 4 K Ca 3 Sc 5 Rb Sr 4 6 Cs Ba Fr 7 Ra 3 Sc Ti V Cr Mn Fe Co Ni Cu Zn 3 Al Si P S Cl Ar 4 Ga Ge As Se Br Kr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd 5 In Sn Sb Te I Xe 6 Cs Ba 5 La Hf Ta W Re Os Ir Pt Au Hg 6 Tl Pb Bi Po At Rn Fr 6 Ac Ra 4 f5 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Be 3 d B C N O F Ne 7 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 He 2 4 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr The electron configuration for Cs: s Or, 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d105s2 5p6 H Ca p [Kr]5s1 Rb Sr 5 The electron configuration for Xe: 1 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 1 p Or, [Xe] 6s1 s 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p66s1 1 H He Be p 2 B C N O F Ne 2 Li 3 Al Si P S Cl Ar 3 Na Mg 3 Al Si P S Cl Ar Ti V Cr Mn Fe Co Ni Cu Zn 4 Ga Ge As Se Br Kr 4 K Ca 3 Sc Ti V Cr Mn Fe Co Ni Cu Zn 4 Ga Ge As Se Br Kr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd 5 In Sn Sb Te I Xe 5 Rb Sr 4 Y Zr Nb Mo Tc Ru Rh Pd Ag Cd 5 In Sn Sb Te I Xe 5 La Hf Ta W Re Os Ir Pt Au Hg 6 Tl Pb Bi Po At Rn 6 Cs Ba 5 La Hf Ta W Re Os Ir Pt Au Hg 6 Tl Pb Bi Po At Rn 6 Ac Fr 6 Ac d 4 f5 7 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Ra 2 d 4 f5 B C N O F Ne Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Page 5 Fall 2009 / UM-SJTU JI Chem 210/ WANG/ Chapter 6C Electron Configuration The electron configuration for La: The electron configuration for Ce: Ce: The electron configuration for Pr: Violations Violations of orbital filling rules occur when lower energy configurations exist. • Certain electron spin subshell subshell arrangements allow lower energy configurations than predicted by normal filling order. • Examples: – half-filled subshells: halfsubshells: • Cr ends with 4s13d5 instead of 4s23d4 4s – completely-filled subshells: completelysubshells: • Cu ends with 4s13d10 instead of 4s23d9 4s Electron Configurations Valence electron configuration for Cf: s The special cases for Hund’s rule: the more stable configurations: Cf = [Rn] 7s2 6d1 5f9 6d0 5f10 valence configuration = 7s25f10 H He 2 Li Be 3 S2 , p6, d10, f14 S1 , p3, d5, f7 S0 , p0 , d0, f0 1 Na Mg 3 Al Si P S Cl Ar 4 K Ca 3 Sc Ti V Cr Mn Fe Co Ni Cu Zn 4 Ga Ge As Se Br Kr 5 Rb Sr 4 Y Zr Nb Mo Tc Ru Rh Pd Ag Cd 5 In Sn Sb Te I Xe 6 Cs Ba 5 La Hf Ta W Re Os Ir Pt Au Hg 6 Tl Pb Bi Po At Rn Fr 6 Ac 7 Ra 2 d 4 f5 p B C N O F Ne Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Page 6 Fall 2009 / UM-SJTU JI Chem 210/ WANG/ Chapter 6C Electron Configuration SAMPLE PROBLEM 2 SAMPLE PROBLEM 1 Quantum Numbers from Orbital Diagrams Write a set of quantum numbers for the third electron and a set for the eighth electron of the F atom. Using the periodic table, give the following for molybdenum (Mo: Z = 42) full configuration condensed configuration 9 F 1s 2s There are ____ inner electrons and ___ valence electrons. 2p valence orbital diagram The 3rd electron is in the 2s orbital; quantum numbers are n= 2 l= 0 ml = 0 ms=+ or -1/2 The 8th electron is in a 2p orbital; quantum numbers are: n=2 l= 1 ml = -1, 0, or +1 ms= + or -1/2 Set of quantum numbers for last valence electron to be filled: n= l= ml = m s= Such Such as (___, ____, ____, _____ ) SAMPLE PROBLEM 3 Using the periodic table, give the full and condensed electrons configurations, partial orbital diagrams showing valence electrons, and number of inner electrons for: lead (Pb: Z = 82) full configuration condensed configuration There are ___ inner electrons and ___ valence electrons. valence orbital diagram Set of quantum numbers for last valence electron to be filled: n= l= ml = m s= Such Such as (____, ____, ____, _____ ) Page 7 Fall 2009 / UM-SJTU JI ...
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This note was uploaded on 07/30/2011 for the course CHEM 210 taught by Professor Zhang during the Spring '09 term at Shanghai Jiao Tong University.

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