The atomic radius of a chemical element is the distance from the centre of the nucleus to the outermost shell of the 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.
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.
Video Atomic radii of the elements (data page)
Atomic radii
Note: All measurements given are in picometers (pm). For more recent data on covalent radii see Covalent radius.
Maps Atomic radii of the elements (data page)
See also
- Atomic radius
- Covalent radius (Single-, double- and triple-bond radii, up to the superheavy elements.)
- Ionic radius
Notes
- 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.
References
Data is as quoted at http://www.webelements.com/ from these sources:
Atomic radius (empirical)
- J.C. Slater (1964). "Atomic Radii in Crystals". J. Chem. Phys. 41: 3199. Bibcode:1964JChPh..41.3199S. doi:10.1063/1.1725697.
Atomic radius (calculated)
- E. Clementi; D.L.Raimondi; W.P. Reinhardt (1967). "Atomic Screening Constants from SCF Functions. II. Atoms with 37 to 86 Electrons". J. Chem. Phys. 47: 1300. Bibcode:1967JChPh..47.1300C. doi:10.1063/1.1712084.
Van der Waals radius
- A. Bondi (1964). "van der Waals Volumes and Radii". J. Phys. Chem. 68: 441. doi:10.1021/j100785a001.
- M. Mantina; A.C. Chamberlin; R. Valero; C.J. Cramer; D.G. Truhlar (2009). "Consistent van der Waals Radii for the Whole Main Group". J. Phys. Chem. A. 113 (19): 5806-12. Bibcode:2009JPCA..113.5806M. doi:10.1021/jp8111556. PMID 19382751.
Covalent radii (single bond)
More recent data can be found in Covalent radius. The above values are based on
- 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.
Triple-bond covalent radii
- S. Riedel; P.Pyykkö, M. Patzschke; Patzschke, M (2005). "Triple-Bond Covalent Radii". Chem. Eur. J. 11 (12): 3511-3520. doi:10.1002/chem.200401299. PMID 15832398. Mean-square deviation 3pm.
- Triple-Bond Covalent Radii Table online
Metallic radius
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
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