Which atom is little hydrogen or helium

Atomic radius / atomic diameter with table

We will deal with the atomic radius or the atomic diameter in this article. It explains what is meant by the atomic radius and the atomic radii and atomic diameters are given for some elements. This article is part of our chemistry division.

In mathematics it is still quite simple: you have a circle and this has a center point (see circle graphic). If you go from the center to the limit of the circle, you have the radius. And if you double the radius, you get the diameter. And it is precisely this concept that we are now transferring to chemistry, namely to the atomic radius. Unfortunately, it's not that easy in chemistry. Because where does an atom actually end? For this reason, another definition has been thought of. Half the distance between the nuclei of two neighboring atoms is called the atomic radius of an element.

The atomic radii increase in the periodic table of the elements (PSE on the following graphic) from top to bottom and from left to right. However, this rule does not apply to the atoms of the noble gases. As the number of protons increases, the forces of attraction of the atomic nucleus on the electron shell increase and the atomic radius decreases as a result. In principle, one can say that the diameter of an atom is in the order of 10-10 m lies. Atomic radii and atomic diameters are usually given in picometers (1pm = 10-12 m). So atoms are tiny.

The periodic table of the elements (click on large format in a new window):

Atomic radii are divided according to the different types of chemical bonds. One distinguishes.

  • Ionic radii: In systems with a predominantly ionic structure, the atoms are assigned ionic radii.
  • Covalent radii: For atoms in molecular compounds characterized as covalent, covalent radii are given.
  • Metal atomic radii: In metals, the atoms have metal atomic radii.
  • Van der Waals radii: Van der Waals forces act between the molecules of covalent compounds; accordingly there are the van der Waals radii.

Atomic radius and atomic diameter table

If you search for the atomic radius or atomic diameter for different elements in different sources, you will quickly be surprised. Because the values ​​vary massively (even with the same reference). For this reason I have put together a table that covers the various values ​​I have found. First of all, I would like to list just a few important elements. The data are in picometers (1pm = 10-12 m).

Table scrollable to the right
elementsymbolAtomic numberAtomic radius in pm
hydrogenH131 - 37,7
lithiumLi3128 - 152
carbonC.676 - 77,2
nitrogenN770 - 71
oxygenO860,4 - 66
sodiumN / A11153,7 - 186
magnesiumMg12141 - 160
aluminumAl13121 - 143
SiliconSi14111 - 117
sulfurS.16104 - 105
ironFe26124 - 132
copperCu29127 - 132

See also atomic radius: aluminum, argon, beryllium, boron, calcium, chlorine, chromium, iron, fluorine, helium, potassium, carbon, lithium, magnesium, sodium, neon, nickel, phosphorus, oxygen, scandium, sulfur, silicon, nitrogen, Titanium, vanadium, hydrogen


  • http://de.wikipedia.org/wiki/Atomradius
  • http://www.uniterra.de/rutherford/tab_atr2.htm
  • http://www.techniklexikon.net/d/atomradius/atomradius.htm
  • http://www.tomchemie.de/wbb2/thread.php?postid=37496
  • Duden: Abitur knowledge chemistry


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