Chapter_18_Notes

Chapter_18_Notes - The d-block Comprises groups 3-12...

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1 The d-block Shriver, Chapter 18 Comprises groups 3-12 Organized into triads (by groups) and series (by row) e.g., Ti, Zr, Hf are the group 4 triad e.g., Sc-Zn are the 3 d series group 3 and group 12 rarely have partly-filled d-shells their behavior is more like the main group (s- and p-blocks) group 4-11 often have partly-filled d-shells (transition metals, TM) their behavior dictated by the d-shell also divided into early TM (groups 4-5), mid-TM (groups 6-8) and late TM (groups 9-11) atomic radii decrease from left to right as the effective nuclear charge increases atomic radii increase from the 2 nd to the 3 rd period the f-block occurs between the 2 nd and 3 rd rows, giving rise to the lanthanide contraction f-electrons do not screen the increased nuclear charge well therefore 2 nd and 3 rd row elements of the same triad are more similar (atomic radius) than the first row element ionization energies increase across the row ionization energies decrease down a group Origin Found in nature as oxides (hard metal cations) or sulfide (soft metal cations) Late TM are soft; early TM are hard (oxophilic) Higher oxidation states are harder than lower oxidation states, for the same metal First row metals are harder than 2 nd , 3 rd row metals Metal oxides are generally reduced with carbon Except Ti (why? carbide?): TiO 2 + C + Cl 2 TiCl 4 + 2 CO TiCl 4 + 2 Mg Ti + MgCl 2 Metal sulfides are “roasted” in air to give the metal (Ni) or metal oxide (ZnO) that is then reduced with C Elements exhibit metallic bonding: filling of the s- and d-bands As d-band is filled, bonding becomes stronger, until half-filled, then more d-electrons are antibonding Therefore metal-metal bond strength is maximum in the mid-TM (group 7) Cs (group 1) 6s 1 mp 29 °C Ba (group 2) 6s 2 mp 725 °C
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2 W (group 6) 4f 14 6d 4 6s 2 mp 3410 °C (refractory) Au (group 11) 5d106s1 mp 1064 °C **Hg (group 12) 5d106s2 mp -39 °C Tl (group 13) 5d 10 6s 2 6p 1 mp 303 °C ** relativistic effects Oxidation states Maximum oxidation state is always equal to the group number Cr VI O 4 2- (chromate), Mn VII O 4 - (permanganate) but Mn VI O 4 2- (manganate), Fe VI O 4 2- (ferrate) max. oxidation state may not be achieved (group 8: OsO 4 , Os(+8), but no +9 in group 9) stability of high oxidation states increase down the group color: metal ions in lower than max. oxidation state are highly colored, because of low- energy d-d transitions in the visible Metal ions in max. oxidation state are often colorless (ReO 4 - ) but this is not always the case: MnO 4 - is bright purple due to ligand-to-metal charge transfer +2, +3 are common in coordination chemistry lower oxidation states found in organometallic compounds with π -acid ligands (like CO) higher oxidation states found in compounds with strong π -donors (like oxo, O 2- ) coordination number increases down a group e.g., Cr(CN) 6 3- but Mo(CN) 8 4- low oxidation state compounds may be ionic (to increase coordination number)
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Chapter_18_Notes - The d-block Comprises groups 3-12...

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