Periodic Trends

Periodic Trends - Periodic Trends: 1. Valence Electrons...

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Periodic Trends: 1. Valence Electrons Electrons in the outer most shell of an atom Valence electrons is equal to group number 2. Effective Nuclear Charge Consider Mg: it has twelve electrons. [Ne] 3s 2 10 electrons in core, 2 valence electrons 12 protons Electrons are being repelled by the other electrons but are attracted by the protons Not all equally Outer electrons are partially blocked/shielded from the nucleus by other electrons Effective nuclear charge: net (+) charge that an electron “sees” Z eff =Z-S Z= number of protons, S= number of shielding electrons For magnesium: Z eff =12-10=2 However, actual number is 3.3. this is because we never know where an electron is located in an atom. Outer electron may spend time closer to the nucleus (see probability plot) meaning it “sees” a larger (+) charge. Z eff increases left to right, increases top to bottom L R trend: Number of core electrons stays the same, protons increases T B trend: slight trend, (z-s) stays the same, larger electron cores don’t shield as well 3. atomic radius distance from the center of the nucleus to the outermost VE in an atom measure in angstroms, 1x10^-10 m increases right to left, increases top to bottom R L trend: decrease in Z eff means less attraction of the electrons to the protons in
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This note was uploaded on 04/03/2008 for the course CHM 113 taught by Professor Anbar during the Spring '06 term at ASU.

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Periodic Trends - Periodic Trends: 1. Valence Electrons...

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