Atomic Radii of the Elements (data Page)
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The atomic radius of a chemical element is the distance from the center of the nucleus to the outermost shell of an electron. Since the boundary is not a well-defined physical entity, there are various non-equivalent definitions of atomic radius. Depending on the definition, the term may apply only to isolated atoms, or also to atoms in condensed matter, covalently bound in molecules, or in ionized and excited states; and its value may be obtained through experimental measurements, or computed from theoretical models. Under some definitions, the value of the radius may depend on the atom's state and context.[1]

Atomic radii vary in a predictable and explicable manner across the periodic table. For instance, the radii generally decrease rightward along each period (row) of the table, from the alkali metals to the noble gases; and increase down each group (column). The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period. These trends of the atomic radii (and of various other chemical and physical properties of the elements) can be explained by the electron shell theory of the atom; they provided important evidence for the development and confirmation of quantum theory.

Note: All measurements given are in picometers (pm). For more recent data on covalent radii see Covalent radius. Just as atomic units are given in terms of the atomic mass unit (approximately the proton mass), the physically appropriate unit of length here is the Bohr radius, which is the radius of a hydrogen atom. The Bohr radius is consequently known as the "atomic unit of length". It is often denoted by a0 and is approximately 53 pm. Hence, the values of atomic radii given here in picometers can be converted to atomic units by dividing by 53, to the level of accuracy of the data given in this table.

atomic number symbol name empirical + Calculated van der Waals Covalent (single bond) Covalent (triple bond) Metallic
1 H hydrogen 25 53 120 32 no data
2 He helium 120 31 140 46 no data
3 Li lithium 145 167 182 133 no data 152
4 Be beryllium 105 112 153 a 102 85 112
5 B boron 85 87 192 a 85 73
6 C carbon 70 67 170 75 60
7 N nitrogen 65 56 155 71 54
8 O oxygen 60 48 152 63 53
9 F fluorine 50 42 147 64 53
10 Ne neon 160 38 154 67 no data
11 Na sodium 180 190 227 155 no data 186
12 Mg magnesium 150 145 173 139 127 160
13 Al aluminium 125 118 184 a 126 111 143
14 Si silicon 110 111 210 116 102
15 P phosphorus 100 98 180 111 94
16 S sulfur 100 88 180 103 95
17 Cl chlorine 100 79 175 99 93
18 Ar argon 71 71 188 96 96
19 K potassium 220 243 275 196 no data 227
20 Ca calcium 180 194 231 a 171 133 197
21 Sc scandium 160 184 211 a 148 114 162 b
22 Ti titanium 140 176 no data 136 108 147
23 V vanadium 135 171 no data 134 106 134 b
24 Cr chromium 140 166 no data 122 103 128 b
25 Mn manganese 140 161 no data 119 103 127 b
26 Fe iron 140 156 no data 116 102 126 b
27 Co cobalt 135 152 no data 111 96 125 b
28 Ni nickel 135 149 163 110 101 124 b
29 Cu copper 135 145 140 112 120 128 b
30 Zn zinc 135 142 139 118 no data 134 b
31 Ga gallium 130 136 187 124 121 135 c
32 Ge germanium 125 125 211 a 121 114
33 As arsenic 115 114 185 121 106
34 Se selenium 115 103 190 116 107
35 Br bromine 115 94 185 114 110
36 Kr krypton no data 88 202 117 108
37 Rb rubidium 235 265 303 a 210 no data 248
38 Sr strontium 200 219 249 a 185 139 215
39 Y yttrium 180 212 no data 163 124 180 b
40 Zr zirconium 155 206 no data 154 121 160
41 Nb niobium 145 198 no data 147 116 146 b
42 Mo molybdenum 145 190 no data 138 113 139 b
43 Tc technetium 135 183 no data 128 110 136 b
44 Ru ruthenium 130 178 no data 125 103 134 b
45 Rh rhodium 135 173 no data 125 106 134 b
46 Pd palladium 140 169 163 120 112 137 b
47 Ag silver 160 165 172 128 137 144 b
48 Cd cadmium 155 161 158 136 no data 151 b
49 In indium 155 156 193 142 146 167
50 Sn tin 145 145 217 140 132
51 Sb antimony 145 133 206 a 140 127
52 Te tellurium 140 123 206 136 121
53 I iodine 140 115 198 133 125
54 Xe xenon no data 108 216 131 122
55 Cs caesium 265 298 343 a 232 no data 265
56 Ba barium 215 253 268 a 196 149 222
57 La lanthanum 195 226 no data 180 139 187 b
58 Ce cerium 185 210 no data 163 131 181.8 c
59 Pr praseodymium 185 247 no data 176 128 182.4 c
60 Nd neodymium 185 206 no data 174 no data 181.4 c
61 Pm promethium 185 205 no data 173 no data 183.4 c
62 Sm samarium 185 238 no data 172 no data 180.4 c
63 Eu europium 185 231 no data 168 no data 180.4 c
64 Gd gadolinium 180 233 no data 169 132 180.4 c
65 Tb terbium 175 225 no data 168 no data 177.3 c
66 Dy dysprosium 175 228 no data 167 no data 178.1 c
67 Ho holmium 175 226 no data 166 no data 176.2 c
68 Er erbium 175 226 no data 165 no data 176.1 c
69 Tm thulium 175 222 no data 164 no data 175.9 c
70 Yb ytterbium 175 222 no data 170 no data 176 c
71 Lu lutetium 175 217 no data 162 131 173.8 c
72 Hf hafnium 155 208 no data 152 122 159
73 Ta tantalum 145 200 no data 146 119 146 b
74 W tungsten 135 193 no data 137 115 139 b
75 Re rhenium 135 188 no data 131 110 137 b
76 Os osmium 130 185 no data 129 109 135 b
77 Ir iridium 135 180 no data 122 107 135.5 b
78 Pt platinum 135 177 175 123 110 138.5 b
79 Au gold 135 174 166 124 123 144 b
80 Hg mercury 150 171 155 133 no data 151 b
81 Tl thallium 190 156 196 144 150 170
82 Pb lead 180 154 202 144 137
83 Bi bismuth 160 143 207 a 151 135
84 Po polonium 190 135 197 a 145 129
85 At astatine no data 127 202 a 147 138
86 Rn radon no data 120 220 a 142 133
87 Fr francium no data no data 348 a no data no data no data
88 Ra radium 215 no data 283 a 201 159 no data
89 Ac actinium 195 no data no data 186 140 no data
90 Th thorium 180 no data no data 175 136 179 b
91 Pa protactinium 180 no data no data 169 129 163 d
92 U uranium 175 no data 186 170 118 156 e
93 Np neptunium 175 no data no data 171 116 155 e
94 Pu plutonium 175 no data no data 172 no data 159 e
95 Am americium 175 no data no data 166 no data 173 b
96 Cm curium 176 no data no data 166 no data 174 b
97 Bk berkelium no data no data no data no data no data 170 b
98 Cf californium no data no data no data no data no data 186±2 b
99 Es einsteinium no data no data no data no data no data 186±2 b
100 Fm fermium no data no data no data no data no data no data
101 Md mendelevium no data no data no data no data no data no data
102 No nobelium no data no data no data no data no data no data
103 Lr lawrencium no data no data no data no data no data no data
104 Rf rutherfordium no data no data no data no data 131 no data
105 Db dubnium no data no data no data no data 126 no data
106 Sg seaborgium no data no data no data no data 121 no data
107 Bh bohrium no data no data no data no data 119 no data
108 Hs hassium no data no data no data no data 118 no data
109 Mt meitnerium no data no data no data no data 113 no data
110 Ds darmstadtium no data no data no data no data 112 no data
111 Rg roentgenium no data no data no data no data 118 no data
112 Cn copernicium no data no data no data no data 130 no data
113 Nh nihonium no data no data no data no data no data no data
114 Fl flerovium no data no data no data no data no data no data
115 Mc moscovium no data no data no data no data no data no data
116 Lv livermorium no data no data no data no data no data no data
117 Ts tennessine no data no data no data no data no data no data
118 Og oganesson no data no data no data no data no data no data

## Notes

• Difference between empirical and experimental data: Empirical data basically means, "originating in or based on observation or experience" or "relying on experience or observation alone often without due regard for system and theory data".[2] It basically means that you measured it through physical observation, and a lot of experiments generating the same results. Although, note that the values are not calculated by a formula. However, often the empirical results then become an equation of estimation. Experimental data on the other hand are only based on theories. Such theoretical predictions are useful when there are no ways of measuring radii experimentally, if you want to predict the radius of an element that hasn't been discovered yet, or it has too short of a half-life.
• The radius of an atom is not a uniquely defined property and depends on the definition. Data derived from other sources with different assumptions cannot be compared.
• + to an accuracy of about 5 pm
• (a) These radii are taken from M. Mantina, A.C. Chamberlin, R. Valero, C.J. Cramer, and D.G. Truhlar, J. Phys. Chem. 2009, 113, 5806.
• (b) 12 coordinate
• (c) gallium has an anomalous crystal structure
• (d) 10 coordinate
• (e) uranium, neptunium and plutonium have irregular structures

## References

1. ^ Cotton, F. A.; Wilkinson, G. (1988). Advanced Inorganic Chemistry (5th ed.). Wiley. p. 1385. ISBN 978-0-471-84997-1.
2. ^ https://www.merriam-webster.com/dictionary/empirical

Data is as quoted at http://www.webelements.com/ from these sources:

• R.T. Sanderson (1962). Chemical Periodicity. New York, USA: Reinhold.
• L.E. Sutton, ed. (1965). "Supplement 1956-1959, Special publication No. 18". Table of interatomic distances and configuration in molecules and ions. London, UK: Chemical Society.
• J.E. Huheey; E.A. Keiter & R.L. Keiter (1993). Inorganic Chemistry : Principles of Structure and Reactivity (4th ed.). New York, USA: HarperCollins. ISBN 0-06-042995-X.
• W.W. Porterfield (1984). Inorganic chemistry, a unified approach. Reading Massachusetts, USA: Addison Wesley Publishing Co. ISBN 0-201-05660-7.
• A.M. James & M.P. Lord (1992). Macmillan's Chemical and Physical Data. MacMillan. ISBN 0-333-51167-0.

Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.