c3—group1—alkali—metals.pptx

Group 1 elementsAlkali metals (IA) Assigned reading materials Rayner-DIC p245-267; p156-158 Optional reading materials Rayner-DIC p253 lithium batteries; p265 11.15 biological aspects Li Na K Rb Cs Fr ns1 Generalization Metallic luster, low density, low hardness, low mp., good electric and thermal conductivity. Weaker metallic bond. Properties of simple substances Occurrence Na: rock salt (NaCl) seawater sylvinite (KCl/NaCl) borax (Na2[B4O5(OH)4]·8H2O) 硼砂 Chile saltpetre (NaNO3) 硝石 K: sylvite (KCl) seawater sylvinite (KCl/NaCl) carnallite (KCl·MgCl2·6H2O) 光卤石 Li, Rb, Cs: various silicate minerals, e.g. spodumene (LiAlSi2O6) 锂辉石 Extraction of sodium – Downs process Extraction of potassium Na(l) + KCl(l) ? K(g) + NaCl(l) At 850 oC K b.p. 766 oC Na b.p. 890 oC The industrial synthesis of NaOH Typical reactions for alkali metals Species of dioxygen species Bond order ν(O-O)/cm-1 d(O-O)/? radical O2+ Dioxygenyl cation 2.5 1905 1.12 radical O2 oxygen 2 1580 1.21 biradical O2- Superoxide dioxide(1-) 1.5 1097 1.33 radical O22- Peroxide Dioxide(2-) 1 802 1.49 no Molecular orbital energy level diagram of O22- Why alkali metals form different oxides? – A thermodynamic viewpoint Why do alkali metals form different oxides? Li2O (LiO0.5) Na2O2 (NaO) KO2 The large alkali metal cations stabilize large low-charge anions. The less polarizing cations (those with low charge density) stabilize larger polarizable anions. Vice versa. The atypical property of lithium Li Na K Rb Cs χp 1.0 0.9 0.8 0.8 0.8 EI1 (kJ/mol) 520 496 419 403 376 Eo(M+/M) (V) -3.04 -2.71 -2.93 -2.98 -3.03 Why Li is the most powerful reducing metal among the alkali metals? Which one, Li or Na, reacts with water more vigorously? Why? The atypical property of lithium Smaller radius results in higher hydration energy Kinetic factors determine the chemical rates M.p. (Li) = 180.54 oC M.p. (Na)