atomiC radii oF the eLements

The simple model of an atom as a hard sphere that can approach

only to a fixed distance from another atom to which it is not bond-

ed has proved useful in interpreting crystal structures and other

molecular properties . The term van der Waals radius, r

vdw

,

was

originally introduced by Pauling as a measure of this atomic size .

Thus in a closely packed structure two non-bonded atoms A and

B will be separated by the sum of their van der Waals radii r

vdw

(A)

and r

vdw

(B) . The set of

van der Waals radii proposed by Pauling

was refined by Bondi (Reference 1) based on crystallographic data,

gas kinetic collision cross sections, and liquid state properties . The

non-bonded contact distances predicted from the recommended

r

vdw

of Bondi have been compared with actual data in the collec-

tion of the Cambridge Crystallographic Data Center by Rowland

and Taylor (Reference 2) and modified slightly . Their recommend-

ed van der Waals radii are given in the third column of this table .

The Cambridge Crystallographic Data Center also makes use

of a set of “covalent radii” to determine which atoms in a crystal

are bonded to each other . Thus two atoms A and B are judged to

be connected by a covalent bond if their separation falls within a

tolerance of ±0 .4 Å of the sum r

cov

(A) + r

cov

(B) . The covalent radii

are given in the fourth column of the table .

references

1 . Bondi, A ., J. Phys. Chem. 68, 441, 1964 .

2 . Rowland, R . S . and Taylor, R ., J. Phys. Chem. 100, 7384, 1996 .

3 . Cambridge Crystallographic Data Center, www .ccdc .cam .ac .uk/prod-

ucts/csd/radii/

Element

Symbol r

vdw

/Å r

cov

/Å

Actinium

Ac

1 .88

Aluminum

Al

1 .35

Americium

Am

1 .51

Antimony

Sb

1 .46

Argon

Ar

1 .88

1 .51

Arsenic

As

1 .85

1 .21

Astatine

At

1 .21

Barium

Ba

1 .34

Berkelium

Bk

1 .54

Beryllium

Be

0 .35

Bismuth

Bi

1 .54

Boron

B

0 .83

Bromine

Br

1 .85

1 .21

Cadmium

Cd

1 .58

1 .69

Cesium

Cs

1 .67

Calcium

Ca

0 .99

Californium

Cf

1 .83

Carbon

C

1 .70

0 .68

Cerium

Ce

1 .83

Chlorine

Cl

1 .75

0 .99

Chromium

Cr

1 .35

Cobalt

Co

1 .33

Copper

Cu

1 .40

1 .52

Curium

Cm

0 .99

Dysprosium

Dy

1 .75

Erbium

Er

1 .73

Europium

Eu

1 .99

Fluorine

F

1 .47

0 .64

Gadolinium

Gd

1 .79

Gallium

Ga

1 .87

1 .22

Germanium

Ge

1 .17

Gold

Au

1 .66

Element

Symbol r

vdw

/Å r

cov

/Å

Hafnium

Hf

1 .57

Helium

He

1 .40

Holmium

Ho

1 .74

Hydrogen

H

1 .09

0 .23

Indium

In

1 .93

1 .63

Iodine

I

1 .98

1 .40

Iridium

Ir

1 .32

Iron

Fe

1 .34

Krypton

Kr

2 .02

Lanthanum

La

1 .87

Lead

Pb

2 .02

1 .54

Lithium

Li

1 .82

0 .68

Lutetium

Lu

1 .72

Magnesium

Mg

1 .73

1 .10

Manganese

Mn

1 .35

Mercury

Hg

1 .55

1 .70

Molybdenum

Mo

1 .47

Neodymium

Nd

1 .81

Neon

Ne

1 .54

Neptunium

Np

1 .55

Nickel

Ni

1 .63

Niobium

Nb

1 .48

Nitrogen

N

1 .55

0 .68

Osmium

Os

1 .37

Oxygen

O

1 .52

0 .68

Palladium

Pd

1 .63

Phosphorus

P

1 .80

1 .05

Platinum

Pt

1 .72

Plutonium

Pu

1 .53

Polonium

Po

1 .68

Potassium

K

2 .75

1 .33

Praseodymium Pr

1 .82

Element

Symbol r

vdw

/Å r

cov

/Å

Promethium

Pm

1 .80

Protactinium

Pa

1 .61

Radium

Ra

1 .90

Rhenium

Re

1 .35

Rhodium

Rh

1 .45

Rubidium

Rb

1 .47

Ruthenium

Ru

1 .40

Samarium

Sm

1 .80

Scandium

Sc

1 .44

Selenium

Se

1 .90

1 .22

Silicon

Si

2 .10

1 .20

Silver

Ag

1 .72

1 .59

Sodium

Na

2 .27

0 .97

Strontium

Sr

1 .12

Sculpture

S

1 .80

1 .02

Tantalum

Ta

1 .43

Technetium

Tc

1 .35

Tellurium

Te

2 .06

1 .47

Terbium

Tb

1 .76

Thallium

Tl

1 .96

1 .55

Thorium

Th

1 .79

Thulium

Tm

1 .72

Tin

Sn

2 .17

1 .46

Titanium

Ti

1 .47

Tungsten

W

1 .37

Uranium

U

1 .86

1 .58

Vanadium

V

1 .33

Xenon

Xe

2 .16

Ytterbium

Yb

1 .94

Yttrium

Y

1 .78

Zinc

Zn

1 .39

1 .45

Zirconium

Zr

1 .56

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