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Periodic Properties of Elements in the Periodic Table

Periodic Properties of Elements in the Periodic Table. Chapter 38. Periodic Table (Modern Form). Periodic Law. The properties of elements are a periodic function of their atomic number. P = F(z). Atomic radii vs. Z. K. Na. Li. Periodic Law.

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Periodic Properties of Elements in the Periodic Table

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  1. Periodic Properties of Elements in the Periodic Table Chapter 38

  2. Periodic Table (Modern Form)

  3. Periodic Law • The properties of elements are a periodic function of their atomic number P = F(z)

  4. Atomic radii vs. Z K Na Li Periodic Law • When elements are arranged in order of atomic number, similar propertiesrecur periodically.

  5. First Ionization Energy Atomic number Periodic Law

  6. Type of Bonding and structure Atomic properties Atomic number Why Periodic Law? Chemical and Physical properties

  7. Variations: • Across a period • Down the group He First I.E. Ne Ar N F P Be O H C Mg Cl S Si Ca B Li Na Al K Atomic number Ionization Energies

  8. Atomic radius K Ca Na Mg Li Be Ar H Ne He

  9. Atomic Radius (pm) 1pm=1x10-12m

  10. Electronegativity F Electronegativity Cl H Ca Li Na K He Ne Ar Atomic number

  11. H 2.1 He - N 3.0 O 3.5 F 4.0 Ne - B 2.0 C 2.5 Be 1.5 Li 1.0 Mg 1.2 Na 0.9 P 2.1 S 2.5 Cl 3.0 Al 1.5 Si 1.8 Ar - K 0.8 Al 1.0 Electronegativity Increase in electronegativity Decrease

  12. Melting Points m.p./oC C 4000 3000 Si 2000 1000 Ca 0 He Ar Ne -1000 0 5 10 15 20 Atomic number

  13. Increase H -259 He -270 Ne -249 N -210 O -218 F -220 B 2300 C 3730 Be 1280 Li 180 Mg 650 Na 97.8 P 44.2 S 119 Cl -101 Al 660 Si 1410 Ar -189 K 63.7 Ca 850 Unit: oC Melting Points

  14. Periodic Variation of Physical Properties • Structure & Bonding • Giant metallic  Giant covalent  Simple molecular

  15. Periodic Variation of Chemical Properties • Formulae of hydrides, oxides, chlorides • Hydrolytic behaviours and explanations

  16. Peiodicity in formulae Moles of Cl atoms per mole of atoms of element 6 4 2 Li Be B C N O F Ne Na Mg Al Si P S Cl Ar

  17. Hydrides Period 2 LiH BeH2 B2H6 CH4NH3 H2O HF Period 3 NaH MgH2 AlH3 SiH4 PH3H2S HCl Covalent with some ionic character Polar covalent Typically Covalent Ionic

  18. NaH + H2O  NaOH + H2 (H- + H2O  OH- + H2) Ionic BeH2 + 2H2O  Be(OH)2 + 2H2 MgH2+ 2H2O  Mg(OH)2 + H2 B2H6 + 6H2O  2H3BO3 + 6H2 AlH3 + 3H2O  Al(OH)3 + 3H2 Covalent with ionic character Be(OH)2, Mg(OH)2, Al(OH)3 are alkaline H3BO3 is acidic Hydrides Hydrolytic behaviour Bonding

  19. CH4 does not dissolve nor react Typically Covalent SiH4 reacts to give SiO2.2H2O + H2 PH3 very slight soluble H H :OH2 Si Si etc + H2 H OH H H H H Hydrides

  20. Polar covalent NH3 + H2O  NH4+ + OH- H2S + H2O  H3O+ + HS- HF + H2O  H3O+ + F- HCl + H2O  H3O+ + Cl- Hydrides Note: From gp4 to gp7 Acidity increases because polarity of bond increase

  21. Check point 38-3 H-O-H + :NH3 OH- + NH4+ H3O+ + Cl- H2O: + H-Cl N is more electronegative, hence more basic than Cl. It reacts with water by donating its lone pair electron. CH4 , due to its non-polar covalent bond, it does not dissolve nor react with water.

  22. Oxides Ionic Basic Na2O Ionic with Covalent character Amphoteric Al2O3 Covalent Acidic CO2 SO2 NO2

  23. O2- + H2O  2OH- Ionic Oxides Na2O(s) + H2O(l)  2NaOH(aq) Li2O(s) + H2O(l)  2LiOH(aq) MgO(s) + H2O(l)  Mg(OH)2(s)

  24. Al2O3 + 6H+ 2Al3+ + 3H2O Al2O3 + 2OH- + 3H2O  2[Al(OH)4]- Amphoteric Oxides BeO + 2H+ Be2+ + H2O BeO + 2OH- + H2O  [Be(OH)4]2-

  25. :O-H H CO2 + H2O  H2CO3 H+ + HCO3- SO2 + H2O  H2SO3 H+ + HSO3- 2NO2 + H2O  HNO3 + HNO2 Covalent Oxides Mechanism of the Hydrolytic behaviour of covalent oxides: O=X+ [O-X-OH]- + H+

  26. Covalent Oxides P4O6 and P4O10 : P4O6(s) + 6H2O(l), cold  4H3PO3(aq) P4O6(s) + 6H2O(l), hot 3H3PO4(aq) + PH3(g) P4O10(s) + 6H2O(l)  4H3PO4(aq) The actual reactions are complicated. The products formed depend on the amount of water present and the conditions of reaction.

  27. - + O O O O O O Cl Cl Cl Cl O O O O O O O O Cl2O7(g)/(l) Cl2O7(s) Covalent Oxides Group VIIA: F2O, Cl2O and Cl2O7 F2O(g) + H2O(l)  2HF(aq) + O2(g) Cl2O(g) + H2O(l)  2HOCl(aq) Cl2O7(l) + H2O(l)  2HClO4(aq)

  28. Check point 38-4 • SiO2 does not react with water. The giant • covalent structure has high lattice energy. • It is not possible to break it down in aqueous • solution.

  29. LiCl BeCl2 BCl3 CCl4 OCl2 ClF NCl3 AlCl3 NaCl MgCl2 SiCl4 S2Cl2 SCl2 PCl5 PCl3 Cl2 Intermediate with covalent character Ionic Covalent Chlorides

  30. Ionic chlorides • Group IA • LiCl, NaCl are not hydrolysed in aqueous solution, neutral solution formed when dissolved. NaCl (s)  Na+(aq) + Cl-(aq), LiCl (s)  Li+(aq) + Cl-(aq) • Group IIA • MgCl2 is not hydrolysed. • Hydrated crystals undergoes hydrolysis when heated. MgCl2.6H2O  MgCl(OH) + 5H2O + HCl

  31. H :O H BeCl2 + 2H2O Be(OH)2 + HCl Intermediate chlorides BeCl2 and AlCl3 : Be2+ and Al3+ High charge/size ratio, strong polarizing power, cation hydrolysis. :OH2 Be2+ AlCl3 + 3H2O  Al(OH)3 + 3HCl

  32. Cl B+ Cl Cl Covalent chlorides Group IIIA BCl3 :OH2 Due to presence of vacant orbital and the polar B-Cl bond. BCl3 reacts vigorously with water to give boric acid, H3BO3 and HCl. BCl3(l) + 3H2O(l)  H3BO3 (aq) + 3HCl(aq)

  33. Cl Cl Si C Cl Cl Cl Cl Cl Cl Covalent chlorides Group 4A : CCl4 and SiCl4 CCl4 does not hydrolyzed by water SiCl4 hydrolyzes. SiCl4(g) + 4H2O(l)  SiO2.2H2O(s) + 4HCl(aq)

  34. H :N-Cl3 :O H Covalent chlorides Group VA: NCl3 NCl3(l) + 3H2O(l)  NH3(aq) + 3HOCl(aq) chloric(I) acid N does not have low-lying vacant orbital, it hydrolyses through the donation of lone pair electron of N atom to the H atom of water molecule.

  35. Covalent chlorides Group VA: PCl3 and PCl5 PCl3(l) + 3H2O(l)  H3PO3(aq) + 3HCl(aq) PCl5(s) + 4H2O(l)  H3PO4(aq) + 5HCl(aq) P is less electronegative than Cl. PCl3 and PCl5 hydrolyze by accepting the electron pair from water molecule.

  36. Covalent chlorides Group VI: SCl2 , S2Cl2 SCl2(g) + H2O(l)  HSCl(aq) + HOCl(aq) S2Cl2(l) + 2H2O(l)  H2S(g) + SO2(g) + 2HCl(aq) Group VII: FCl, Cl2 FCl(g) + H2O(l)  HF(aq) + HOCl(aq) Cl2(g) + H2O(l)  HCl(aq) + HOCl(aq)

  37. Check point 38-5 • Give the equation for the reaction between the • following compounds with water: • AlCl3 • Cl2O6

  38. Past paper questions Periodicity 1999 IIA 3c 2001 IIA 3c

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