Ionic radii and covalent radii

periodicity of elements ionic radii and covalent radii.

1. Periodicity of Elements:Covalent and ionic radius Dr. Mithil Fal Desai Shree Mallikarjun and Shri Chetan Manju Desai College Canacona Goa

2. Covalent radius Covalent radius is the half the inter-nuclear distance between two atoms that are covalently bonded. e - e - 2r X atom X atom

3. Periodic trend in Covalent radii H 30 He Li 123 Be 89 B 90 C 77 N 75 O 73 F 71 Ne Na 157 Mg 136 Al 130 Si 118 P 110 S 102 Cl 99 Ar K 203 Ca 174 Sc 144 Ti 122 V 122 Cr 117 Mn 117 Fe 117 Co 116 Ni 115 Cu 117 Zn 125 Ga 125 Ge 122 As 121 Se 114 Br 114 Kr 200 Rb 216 Sr 191 Y 162 Zr 135 Nb 134 Mo 129 Tc - Ru 124 Rh 125 Pd 128 Ag 134 Cd 141 In 150 Sn 140 Sb 141 Te 137 I 133 Xe 220 Cs 235 Ba 198 La 169 Hf 144 Ta 134 W 130 Re 128 Os 126 Ir 126 Pt 129 Au 134 Hg 144 Tl 155 Pb 146 Bi 152 Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Ce 165 Pr 164 Nd 164 Pm - Sm 166 Eu 185 Gd 161 Tb 159 Dy 159 Ho 158 Er 157 Tm 156 Yb 170 Lu 156 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Radius values in pm Increases Decreases

4. Ionic radius Ionic radius of element is related to the distance b etween centres of neighboring atoms (cation and anion) which share an ionic bond. e - e - e - e - e - e - e - e - r + R X Y X + Y -

5. Periodic trend in ionic radii (+1) (+2) H (-2) (-1) He Li 90 Be 59 B C N O 126 F 119 Ne Na 116 Mg 86 Al Si P S 170 Cl 167 Ar K 152 Ca 114 Sc 88 Ti 74 V Cr Mn Fe Co Ni Cu 91 Zn 88 Ga 76 Ge As Se 184 Br 182 Kr Rb 166 Sr 132 Y Zr Nb Mo Tc Ru Rh Pd Ag 108 Cd 190 In 94 Sn Sb Te 207 I 206 Xe Cs 181 Ba 149 La 117 Hf Ta W Re Os Ir Pt Au 151 Hg 116 Tl 102 Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 100 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Radius values in pm Increases Decreases

6. Ionic radii (continue) Na (186 pm) and Na + (102 pm) Fe( 117 pm ); Fe +2 (78.0 pm ) and Fe +3 (64.5 pm) Cl(99 pm) and Cl - ( 184pm) Ba +2 149 pm and 156 pm for coordination number 6 and 8, respectively

7. Points to remember Covalent radius and ionic radius Decreases in along the row as atomic number increases. Increases down the group as atomic number increases . The ionic radius of cation is smaller than covalent radius. The ionic radius of a nion is bigger than covalent radius . The coordination number affects the ionic radius of the atom.