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Periodic Properties of Elements in the Periodic Table Chapter 38.

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Presentation on theme: "Periodic Properties of Elements in the Periodic Table Chapter 38."— Presentation transcript:

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

5 Periodic Law Atomic number First Ionization Energy

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

7 Ionization Energies H He Ne Ar LiNa K N Be B C O F Mg P Al Si S Cl Ca Atomic number First I.E. Variations: 1.Across a period 2.Down the group

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

9 H 37 He 54 Li 156 Be 105 B 91 C 77 N 71 O 60 F 67 Ne 80 Na 186 Mg 160 Al 143 Si 117 P 111 S 104 Cl 99 Ar 96 K 231 Ca 197 Sc 161 Ti 154 V 131 Cr 125 Mn 118 Fe 125 Co 125 Ni 124 Cu 128 Zn 133 Ga 123 Ge 122 As 116 Se 115 Br 114 Kr 99 Rb 243 Sr 215 Y 180 Zr 161 Nb 147 Mo 136 Tc 135 Ru 132 Rh 132 Pd 138 Ag 144 Cd 149 In 151 Sn 140 Sb 145 Te 139 I 138 Xe 109 Cs 265 Ba 210 Hf 154 Ta 143 W 137 Re 138 Os 134 Ir 136 Pt 139 Au 144 Hg 147 Tl 189 Pb 175 Bi 155 Po 167 At 145 Rn La 187 Ce 183 Pr 182 Nd 181 Pm 181 Sm 180 Eu 199 Gd 179 Tb 176 Dy 175 Ho 174 Er 173 Tm 173 Yb 194 Lu 172 Atomic Radius (pm) 1pm=1x m

10 Electronegativity H HeNeAr F Cl Li Na K Ca Electronegativity Atomic number

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

12 Melting Points m.p./ o C Atomic number C Si He Ne Ar Ca

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

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 Li Be B C N O F Ne Na Mg Al Si P S Cl Ar Moles of Cl atoms per mole of atoms of element

17 Hydrides Period 2LiH BeH 2 B 2 H 6 CH 4 NH 3 H 2 O HF Period 3NaH MgH 2 AlH 3 SiH 4 PH 3 H 2 S HCl Ionic Covalent with some ionic character Typically Covalent Polar covalent

18 Hydrides Bonding Hydrolytic behaviour Ionic NaH + H 2 O NaOH + H 2 (H - + H 2 O OH - + H 2 ) Be(OH) 2, Mg(OH) 2, Al(OH) 3 are alkaline H 3 BO 3 is acidic Covalent with ionic character BeH 2 + 2H 2 O Be(OH) 2 + 2H 2 MgH 2 + 2H 2 O Mg(OH) 2 + H 2 B 2 H 6 + 6H 2 O 2H 3 BO 3 + 6H 2 AlH 3 + 3H 2 O Al(OH) 3 + 3H 2

19 Hydrides Typically Covalent CH 4 does not dissolve nor react SiH 4 reacts to give SiO 2.2H 2 O + H 2 PH 3 very slight soluble Si H H H H :OH 2 Si H H OH H + H 2 etc

20 Hydrides Polar covalent NH 3 + H 2 O NH OH - H 2 S + H 2 O H 3 O + + HS - HF + H 2 O H 3 O + + F - HCl + H 2 O H 3 O + + Cl - Note: From gp4 to gp7 Acidity increases because polarity of bond increase

21 Check point 38-3 H-O-H:NH 3 OH - + NH H 2 O:+ H-Cl H 3 O + + Cl - N is more electronegative, hence more basic than Cl. It reacts with water by donating its lone pair electron. CH 4, due to its non-polar covalent bond, it does not dissolve nor react with water.

22 Oxides Ionic Ionic with Covalent character AmphotericAl 2 O 3 Covalent Acidic CO 2 SO 2 NO 2 Basic Na 2 O

23 Ionic Oxides O 2- + H 2 O 2OH - Na 2 O(s) + H 2 O(l) 2NaOH(aq) Li 2 O(s) + H 2 O(l) 2LiOH(aq) MgO(s) + H 2 O(l) Mg(OH) 2 (s)

24 Amphoteric Oxides Al 2 O 3 + 6H + 2Al H 2 O Al 2 O 3 + 2OH - + 3H 2 O 2[Al(OH) 4 ] - BeO + 2H + Be 2+ + H 2 O BeO + 2OH - + H 2 O [Be(OH) 4 ] 2-

25 Covalent Oxides O=X + :O-H H [O-X-OH] - + H + Mechanism of the Hydrolytic behaviour of covalent oxides: CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - SO 2 + H 2 O H 2 SO 3 H + + HSO 3 - 2NO 2 + H 2 O HNO 3 + HNO 2

26 Covalent Oxides P 4 O 6 and P 4 O 10 : P 4 O 6 (s) + 6H 2 O(l), cold 4H 3 PO 3 (aq) P 4 O 6 (s) + 6H 2 O(l), hot 3H 3 PO 4 (aq) + PH 3 (g) P 4 O 10 (s) + 6H 2 O(l) 4H 3 PO 4 (aq) The actual reactions are complicated. The products formed depend on the amount of water present and the conditions of reaction.

27 Covalent Oxides Group VIIA: F 2 O, Cl 2 O and Cl 2 O 7 F 2 O(g) + H 2 O(l) 2HF(aq) + O 2 (g) Cl 2 O(g) + H 2 O(l) 2HOCl(aq) Cl 2 O 7 (l) + H 2 O(l) 2HClO 4 (aq) Cl O O O O O O O Cl 2 O 7 (g)/(l) Cl O O O O O O O + - Cl 2 O 7 (s)

28 Check point 38-4 a.SiO 2 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 Chlorides LiCl NaCl MgCl 2 Ionic AlCl 3 BeCl 2 Intermediate with covalent character BCl 3 CCl 4 SiCl 4 NCl 3 PCl 5 PCl 3 OCl 2 S 2 Cl 2 SCl 2 ClF Cl 2 Covalent

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 MgCl 2 is not hydrolysed. Hydrated crystals undergoes hydrolysis when heated. MgCl 2.6H 2 O MgCl(OH) + 5H 2 O + HCl

31 Intermediate chlorides BeCl 2 and AlCl 3 : Be 2+ and Al 3+ High charge/size ratio, strong polarizing power, cation hydrolysis. Be 2+ :O H H :OH 2 Be(OH) 2 + HClBeCl 2 + 2H 2 O AlCl 3 + 3H 2 O Al(OH) 3 + 3HCl

32 Covalent chlorides Group IIIA BCl 3 Cl B + :OH 2 Due to presence of vacant orbital and the polar B-Cl bond. BCl 3 reacts vigorously with water to give boric acid, H 3 BO 3 and HCl. BCl 3 (l) + 3H 2 O(l) H 3 BO 3 (aq) + 3HCl(aq)

33 Covalent chlorides Group 4A : CCl 4 and SiCl 4 Cl Si Cl C CCl 4 does not hydrolyzed by water SiCl 4 hydrolyzes. SiCl 4 (g) + 4H 2 O(l) SiO 2.2H 2 O(s) + 4HCl(aq)

34 Covalent chlorides Group VA: NCl 3 NCl 3 (l) + 3H 2 O(l) NH 3 (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. :O H H :N - Cl 3

35 Covalent chlorides Group VA: PCl 3 and PCl 5 PCl 3 (l) + 3H 2 O(l) H 3 PO 3 (aq) + 3HCl(aq) PCl 5 (s) + 4H 2 O(l) H 3 PO 4 (aq) + 5HCl(aq) P is less electronegative than Cl. PCl 3 and PCl 5 hydrolyze by accepting the electron pair from water molecule.

36 Covalent chlorides Group VI: SCl 2, S 2 Cl 2 SCl 2 (g) + H 2 O(l) HSCl(aq) + HOCl(aq) S 2 Cl 2 (l) + 2H 2 O(l) H 2 S(g) + SO 2 (g) + 2HCl(aq) Group VII: FCl, Cl 2 FCl(g) + H 2 O(l) HF(aq) + HOCl(aq) Cl 2 (g) + H 2 O(l) HCl(aq) + HOCl(aq)

37 Check point 38-5 Give the equation for the reaction between the following compounds with water: a.AlCl 3 b.Cl 2 O 6

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


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