Ch 8.6--10.7

Ch 8.6--10.7 - Chem 8.610.7 A 8.6 Periodic Trends in Size...

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Chem. 8.6—10.7 A. 8.6 Periodic Trends in Size of Atoms and Effective Nuclear Charge a. atomic radius is determined: a.i. way of nonbonding atomic radius or van der Waals radius : the distance between nonbonding atoms that are in direct contact a.ii. bonding atomic radius or covalent radius : a.ii.1. nonmetals: ½ the distance between 2 of atoms bonded together a.ii.2. metals: ½ the distance between 2 atoms next to each other in a crystal of metal b. atomic radius : set of average bonding radii determined from measurements on large number of elements + compounds b.i. represents the radius of an atom when bonded to another atom + always smaller than van der Waals radius b.ii. bond length of 2 covalently bonded atoms: sum of atomic radii b.iii. largely dependent on valence electrons b.iv. trend: b.iv.1. as move down a column/family, atomic radius increases (bigger atoms/larger orbitals) b.iv.2. as move to right across a period (row) in period, atomic radius decreases b.iv.2.a. effective nuclear charge (Z eff ) experienced by electrons in outermost principal energy level increases as move down a row, resulting in stronger attraction b/w outermost electrons + nucleus b.iv.2.b. this is because the nucleus becomes more positive, but the # of core electrons shielding remains the same (for same period since outer electrons don’t shield other outer electrons) so Z eff increases, c. Effective Nuclear Charge: avg/net charge experienced by an electron c.i. Z eff = Z – S c.i.1. (Z) actual nuclear charge c.i.2. (S) charge screened by other electrons c.ii. Core electrons efficiently shield electrons in outermost principal energy level from nuclear charge, but outermost electrons do not efficiently shield one another from nuclear charge d. Atomic Radii and Transition Elements d.i. with exception of first couple of elements in transition metals, they generally don’t follow the same trend d.ii. radii of transition elements stay roughly constant across each row d.ii.1. this is b/c across row of transition elements number of electrons in outermost principal energy level is nearly constant (since 4s orbitals fill before 3d) d.ii.2. electrons added in transition elements is added to (n-1) d orbitals, so about the same Z eff
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B. 8.7 Ions: Electron Configurations, Magnetic Properties, Ionic Radii and Ionization Energy a. Electron Configurations + Magnetic Properties of Ions a.i. for monoatomic ions, to deduce electronic configuration, still add/subtract electrons to fit the charge a.i.1. electrons are removed from highest n=value orbital first, even if doesn’t correspond to reverse order of filling a.ii. for transition metal cations, order in which electrons are removed upon ionization = not reverse of filling order since ns and ( n -1) d orbitals = very close to each other + b/c ns are higher up in energy level than (n-1) d b. magnetic properties of transition metal ions support this^ b.i. paramagnetic : when an atom/ion contains unpaired electrons is attracted
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Ch 8.6--10.7 - Chem 8.610.7 A 8.6 Periodic Trends in Size...

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