Chapter5_11 - these two states would be degenerate....

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PHY4604 R. D. Field Department of Physics Chapter5_11.doc University of Florida The Periodic Table “Shell” Structure: The n th energy level (called a “shell”) has n possible l values and each l has 2 l -1 possible m values. Hence n th shell has n 2 states and each state can hold two electrons (one with s z = +½ and one with s z = - ½). Shell l values Number of States Maximum Number of Electrons 1 0 1 2 2 1,0 3+1=4 8 3 2,1,0 5+3+1=9 18 n th n-1, n-2,. ..,0 n 2 2n 2 Periodic Table: After hydrogen and helium comes lithium with Z = 3. The n = 1 shell is filled with two of the electrons and the third electron has to go into n = 2 (with l = 1 or 0). In the absence of electron-electron interactions
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Unformatted text preview: these two states would be degenerate. However, because of electron screening the lower energy state is occurs for l = 0 corresponding to a 2 S 1/2 state. The next element is beryllium with Z = 4 and electrons (1s) 2 (2s) 2 and since l = 0 the state is 1 S . Z Element Ground State Configuration 1 1 H 1 (1s) 1 2 S 1/2 2 4 He 2 (1s) 2 1 S 3 7 Li 3 (1s) 2 (2s) 1 2 S 1/2 4 9 Be 4 (1s) 2 (2s) 2 1 S 5 11 B 5 (1s) 2 (2s) 2 (2p) 1 2 P 1/2 6 12 C 6 (1s) 2 (2s) 2 (2p) 2 3 P 7 14 N 7 (1s) 2 (2s) 2 (2p) 3 4 S 3/2 8 16 O 8 (1s) 2 (2s) 2 (2p) 4 3 P 2 9 19 F 9 (1s) 2 (2s) 2 (2p) 5 2 P 3/2 10 20 Ne 10 (1s) 2 (2s) 2 (2p) 6 1 S...
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