Electron in a p orbital of the same n value

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electron in a p orbital of the same “n” value Explanation of trend irregularities”: Mg to Al 10p+ 2s 2p n = 2 n = 1 3s 3p n = 3 Mg: 1 s 2 2 s 2 2 p 6 3 s 2 atomic number of element 0 5 10 15 20 first ionization energy 0 500 1000 1500 2000 2500 Be Mg Al B C N O F Si P S Cl Ne Li Na Ar He H 36 S. Ensign, periodic properties 1s 2s 3s 2p 3p Al A filled s orbital provides some shielding of the nuclear charge felt by an electron in a p orbital of the same “n” value 10p+ 2s 2p n = 2 n = 1 3s 3p n = 3 Al: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 1 Explanation of trend irregularities”: Mg to Al
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1s 2s 2p S. Ensign, periodic properties 37 Explanation of trend irregularities: N to O and P to S O: 1 s 2 2 s 2 2 p 4 N: 1 s 2 2 s 2 2 p 3 1s 2s 2p The e - configuration np 3 (a “spin party”) is good 1s 2s 3s 2p 3p S. Ensign, periodic properties 38 Explanation of trend irregularities: N to O and P to S S: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 4 P: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 3 1s 2s 3s 2p 3p The e - configuration np 3 (a “spin party”) is good 39 Electron affinity (EA) The energy change associated with the addition of an electron to a gaseous atom or ion (-) E.A. : E is released (usually, but not always the case) (+) E.A. : E is added X + (g) + e - Æ X (g) X (g) + e - Æ X - (g) When reported with units of kJ/mol, it is the energy change associated with adding one mol of electrons to one mol of gaseous atoms or ions S. Ensign, periodic properties 40 Electron affinity values/trends More negative EA (in general) ex. n = 2, 5 and 8 Not much change in EA (in general) S. Ensign, periodic properties
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41 Z p+ - - - Why the trends in electron affinity values? More negative EA (in general) Not much change in EA (in general) S. Ensign, periodic properties S. Ensign, periodic properties 42 Explanation for why group 2A elements have positive or small negative electron affinities 10p+ 2s 2p n = 2 n = 1 3s 3p n = 3 Mg: 1 s 2 2 s 2 2 p 6 3 s 2 Add e - .. S. Ensign, periodic properties 43 Explanation for why group 6A elements have positive or “out of pattern” negative electron affinities 1s 2s 2p N - : 1 s 2 2 s 2 2 p 4 N: 1 s 2 2 s 2 2 p 3 1s 2s 2p The e - configuration np 3 (a “spin party”) is good e -
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