Chapter 6 Electronic Structure of Atoms Prepare for Recitation September 8th ALEKS Objective 2 due September 6th ANGEL Quiz 2 September 8th Lecture 5 August 31st Lecture 6 September 2nd Labor Day Holiday September 5th You are advised to re read Ch 6 1 6 6 in addition to the work shown below in order to help you see the big picture for this section of the course Read Ch 6 7 6 9 Additional Preparation BLB 6 33 39 54 Packet 6 6 9 ALEKS work is necessary but not sufficient for exam level preparation Do not neglect the packet CH110 FA11 SAS 1 Chapter 6 Electronic Structure of Atoms KEY QUESTIONS THE BIG PICTURE What is the structure of an atom What are the properties of atoms Remember structure affects function Where are the electrons located What is the energy of an electron By the end of Today s Lecture you should know wavelength and frequency of light dual nature of light electronic transitions and line spectra Bohr model Matter acts as waves Heisenberg Uncertainty Principle Electronic transitions of orbitals Quantum numbers n m ms Orbitals their shapes and energies Orbitals and atoms with many electrons Spin quantum number ms Pauli Exclusion Principle and Hunds Rule Electron Configurations using the periodic table CH110 FA11 SAS 2 Concept Check Understanding electromagnetic energy led to quantum theory it explains what we observe which led to atomic structure and predicts electron configurations and explains periodic trends of the elements CH110 FA11 SAS 3 Why do Orbital Energies Differ Quantitatively Electrons in inner orbitals act as screens for outer electrons Outer electrons experience a lesser nuclear charge less attraction General Trends in Screening For a given shell defined by s orbital has electron density at nucleus sees larger Zeff and p orbital has no electron density at the nucleus and screening increases E increases CH110 FA11 SAS 4 Energies of Orbitals Many Electron Atoms Questions we haven t answered yet How do the electrons fill the orbitals In what order How many electrons can go into an orbital CH110 FA11 SAS 5 Electron spin Stern Gerlach experiment neutral atoms electrons seem to possess magnetic moment that is quantized enter another quantum number spin magnetic quantum number CH110 FA11 SAS 6 The Fourth Quantum Number ms Electron has spin as if it had north and south poles Confirmed by Experiment ms Pauli Exclusion Principle Electrons have 4 quantum numbers n l ml ms define orbital Wolfgang Pauli 1945 Nobel Prize in Physics ms has only 2 spin values and no two ecan have the same 4 quantum numbers Therefore max of 2 electrons per orbital CH110 FA11 SAS 7 Pauli Exclusion Principle No two electrons in an atom can have the same four quantum numbers Electrons in the same orbital have the same values for the first three quantum numbers ms can have only two values An orbital can hold only two electrons Subshell s l 0 p l 1 d l 2 f l 3 No of Orbitals Max No of e Look at the periodic table CH110 FA11 SAS 8 Why Does the Periodic Table Look Like it Does Because of the Pauli Exclusion Principle The Aufbau Principle H He Li Be B C CH110 FA11 SAS 9 Hunds Rule How do we fill orbitals of equal energy same with electrons How do we handle ms of the electrons Carbon 1s2 2s2 6 electrons 2p2 Why How do you keep electrons apart which minimizes their energy CH110 FA11 SAS 10 Practice Problem Fill in the following table in accordance with Hunds Rule 1s 2s 2p 3s C N O Ne Na CH110 FA11 SAS 11 Electron Configurations Memorize Orbitals are filled by electrons in sequence determined by energy H He Li Be B C N O F Ne Na Mg 1s 1s2 1s22s new row of Periodic Table 1s22s2 1s22s22p 1s22s22p2 1s22s22p3 1s22s22p4 1s22s22p5 1s22s22p6 1s22s22p63s new row of PT 1s22s22p63s2 CH110 FA11 SAS 12 More Electron Configurations Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn 1s22s22p6 filled shell Ne 3s new row of PT Ne 3s2 Ne 3s23p Ne 3s23p2 Ne 3s23p3 Ne 3s23p4 Ne 3s23p5 Ne 3s23p6 Ar 4s new row of PT Ar 4s2 Ar 4s23d Ar 4s23d2 Ar 4s23d3 Ar 4s13d5 Ar 4s23d5 transition 2 6 Ar 4s 3d metals 2 7 Ar 4s 3d Ar 4s23d8 Ar 4s13d10 Ar 4s23d10 CH110 FA11 SAS 13 Electron Configuration and the Periodic Table Location on the periodic table is related to electron configuration Elements in the same column family have the same configuration Example alkali metals column 1 have what valence electron configuration H Li Na K Rb Cs He Ne Ar Kr Xe halogens F Cl Br I have outer shell noble gases inert have filled outer shell of Valence electrons determine the chemistry CH110 FA11 SAS 14 Electron Configurations of the Elements CH110 FA11 SAS 15 Practice Problem Which of the following electron configurations can be ruled out by the Pauli Exclusion Principle A 1s22s22p63s23p64s13d7 B 1s22s22p63s23p64s23d5 C 1s22s22p63s23p64s24d6 D 1s22s22p63s23p64s23d6 E 1s22s22p83s23p64s23d3 CH110 FA11 SAS 16 Practice with Electron Configurations CH110 FA11 SAS 17 The d Shell Exceptions Half filled and completely filled d shells are stabilizing and electrons will move to achieve this in the Cr and Cu groups What is the electron configuration of copper in its ground state Fill in the energy diagram for copper in its ground state CH110 FA11 SAS 18 What You Should Know Electrons in atoms are quantized Describe the set of 4 quantum numbers needed to uniquely describe any e Quantum numbers describe size shape and orientation of orbitals and the spin of the electron Know which describes each of these What is the Pauli Exclusion Principle Energy Level Diagrams H atom vs many electron atoms which orbitals are degenerate Be able to place the orbitals in order of increasing energy Explain why H and many electron atoms are different CH110 FA11 SAS 19 What You Should Know Electrons Configurations What is Hund s rule and why does it determine the most stable configuration Write the electron configuration of any element Write electron configurations using condensed notation noble gas in brackets Know the difference between core and valence electrons Recognize the half filled or full shell exceptions to our general rules Know how to use the periodic table to determine electron configurations CH110 FA11 SAS 20
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