Lecture 4 Electronic structure of an atom Read HW BLB 6 3 6 6 BLB 6 33 39 51 54 Sup 6 6 7 8 10 no Sup 6 9 Know matter waves uncertainty principle electronic transitions of orbitals quantum numbers n m ms orbitals their shapes and energies Drop add ends TODAY Wednesday Jan 21 Bonus deadline for Skill Check Tests 3 4 is Jan 29 Thursday Exam 1 Monday Feb 9 6 30 Form a study group use the CRC take advantage of SI info on web use the online resources and work those problems practice practice practice Sheets s office hours Mondays 12 30 2 Tuesdays 10 30 12 in 324 Chem or 326 Chem Sheets Page 1 Lecture 4 Dual nature of electrons Bohr model explained some experimental evidence for H atom but it failed for other atoms why was this DeBroglie if light has a dual wave particle nature then why doesn t matter have a dual wave particle nature hmmm h mv m mass v velocity h Planck s constant NOTE mv momentum particle nature and referred to as a matter wave wave nature effects observable only for extremely small mass for a baseball or bacteria is too small to observe but for e is of atomic size producing profound effects electron waves discovered in 1927 Davidson Garmer basis for electron microscope electrons diffract when interacting with matter Sheets Page 2 Lecture 4 Heisenberg uncertainty principle derives from wavelike nature of matter it is NOT possible to simultaneously know the position velocity momentum mv of a particle with complete certainty this really becomes important when dealing with subatomic matter all electrons have a velocity therefore you cannot specify their exact location it s not appropriate to imagine e moving in nice little orbits around the nucleus contradicts Bohr s planetary model of H atom so can we say anything about where the e are Sheets Page 3 Lecture 4 The Schr dinger wave equation takes into account both particle wave terms H E x y z wave function shape but 2 x y z probability of finding one e in a region of space that is referred to as or probability density electrons in atoms behave as standing waves think of e as clouds of e density Sheets Page 4 Lecture 4 The Schr dinger wave equation cont orbitals 2 x y z modern view of atomic structure specify probability of finding an e in a given region of space i e have specify of that e are characterized by 3 different quantum numbers Sheets Page 5 Lecture 4 Figure from Moore Stanitski Jurs 2005 Chemistry The Molecular Science Thomson Brooks Cole Sheets Page 6 Lecture 4 Quantum numbers 1 principal quantum number n determines info about the shell modern equivalent to n in Bohr model n intergers 2 azimuthal quantum number determines info about orbital NOTE use symbols rather than numbers for 0 1 2 3 name 3 magnetic quantum number m determines orbital s 3D a range of numbers m Sheets including 0 Page 7 Lecture 4 Review of orbitals orbitals region of space with size shape and characteristic energy orbital name of orbitals s 0 shape sphere radially symmetric p 1 dumbbell 2 lobes node in center d 2 clover 1 2 lobes collar different from p orbitals f 3 node 2 0 yikes note E as nodes check out http www weizmann ac il home comartin orbitals html the Grand Orbital Table is nifty Sheets Page 8 Lecture 4 Even more about orbitals shell defined by quantum number subshell defined by e g 3s 2p n quantum numbers n n 3 0 n 2 1 when orbitals of the same subshell have the same energy they are degenerate orbital defined by e g quantum numbers n m 2px n 2 1 2py n 2 1 2pz n 2 1 and m 1 0 1 when 1 NOTE all of these have the same energy Sheets Page 9 Lecture 4 More about orbitals e g 3d n 3 m orbitals in subshell recall higher energy more nodes e g BLB Fig 6 18 node 2 0 note E as nodes n2 total number of orbitals in the nth shell see BLB Table 6 2 you now know enough to make up this table Sheets Page 10 Lecture 4 Before next class Read HW BLB 6 7 6 9 BLB 6 59 63 67 71 74 75 90 97 Sup 6 11 15 Know orbitals atoms with 1 electrons Pauli exclusion principle Hund s rule electronic configurations of atoms Sheets Page 11 Lecture 4
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