Periodic Properties Of Elements In The Periodic Table

Periodic Properties of Elements in the Periodic Table Chapter 38

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

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

Periodic Law Atomic number First Ionization Energy

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

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

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

Atomic Radius (pm) 1pm=1x10 -12 m Lu 172 Yb 194 Tm 173 Er 173 Ho 174 Dy 175 Tb 176 Gd 179 Eu 199 Sm 180 Pm 181 Nd 181 Pr 182 Ce 183 La 187 Rn At 145 Po 167 Bi 155 Pb 175 Tl 189 Hg 147 Au 144 Pt 139 Ir 136 Os 134 Re 138 W 137 Ta 143 Hf 154 Ba 210 Cs 265 Xe 109 I 138 Te 139 Sb 145 Sn 140 In 151 Cd 149 Ag 144 Pd 138 Rh 132 Ru 132 Tc 135 Mo 136 Nb 147 Zr 161 Y 180 Sr 215 Rb 243 Kr 99 Br 114 Se 115 As 116 Ge 122 Ga 123 Zn 133 Cu 128 Ni 124 Co 125 Fe 125 Mn 118 Cr 125 V 131 Ti 154 Sc 161 Ca 197 K 231 Ar 96 Cl 99 S 104 P 111 Si 117 Al 143 Mg 160 Na 186 Ne 80 F 67 O 60 N 71 C 77 B 91 Be 105 Li 156 He 54 H 37

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

Electronegativity Increase in electronegativity Decrease 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 -

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

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

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

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

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

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

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

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

Hydrides Note: From gp4 to gp7 Acidity increases because polarity of bond increase Polar covalent NH 3 + H 2 O  NH 4 + + 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 -

Check point 38-3 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. H-O-H :NH 3 OH - + NH 4 + + H 2 O: + H-Cl H 3 O + + Cl -

Oxides Ionic Ionic with Covalent character Amphoteric Al 2 O 3 Covalent Acidic CO 2 SO 2 NO 2 Basic Na 2 O

Ionic Oxides 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) O 2- + H 2 O  2OH -

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

Covalent Oxides O=X  + [O-X-OH] - + H + Mechanism of the Hydrolytic behaviour of covalent oxides: :O-H H 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

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.

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 Cl O O O Cl 2 O 7 (g)/(l) Cl O O O O Cl O O O + - Cl 2 O 7 (s)

Check point 38-4 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.

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

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

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

Covalent chlorides Group IIIA BCl 3 :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) Cl Cl Cl B  +

Covalent chlorides Group 4A : CCl 4 and SiCl 4 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) Cl Cl Cl Cl Si Cl Cl Cl Cl C

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

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.

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)

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

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

Periodic Properties Of Elements In The Periodic Table

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Periodic Properties Of Elements In The Periodic Table