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9-Periodic Trends in Elemental Properties

9-Periodic Trends in Elemental Properties - 5.111 Lecture...

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5.111 Lecture Summary #9 September 28, 2009 9.1 Reading for today: Sections 1.14-1.18, 1.20 Reading for Lecture 10: Sections 2.14-2.16, 2.5 PERIODIC TRENDS IN ELEMENTAL PROPERTIES PERIODIC TABLE Assembled by Mendeleev (1870) and others based on similarity of chemical and physical properties of elements. (Mendeleev left space for missing elements – about 1/3 of the naturally occurring elements were unknown!) For example: Li, Na, K originally grouped together in a column because they are all soft, malleable, reactive metals He, Ne, Ar grouped together because of their inertness Elements that are in the same column have related valence e configurations Li, Na, K have a single valence e in an s state He, Ne, Ar have filled shells PERIODIC TRENDS IONIZATION ENERGY (IE) B(1s 2 2s 2 2p 1 ) ⎯⎯⎯ B + (1s 2 2s 2 ) + e Δ E = E pro – E react = IE IE first ionization energy: energy to remove an e from HOAO, most weakly bound e B + (1s 2 2s 2 ) ⎯⎯⎯ B +2 (1s 2 2s 1 ) + e Δ E = IE 2 IE 2 second ionization energy B +2 (1s 2 2s 1 ) ⎯⎯⎯ B +3 (1s 2 ) + e Δ E = IE 3 IE 3 third ionization energy B +3 (1s 2 ) ⎯⎯⎯ B +4 (1s 1 ) + e Δ E = IE
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