Atom Sizes

All atoms are about the same size as each other. You would think that heavy atoms, with many electrons, would be much larger, but they aren't.

The reason is that large atoms have large nuclei with many protons. These exert a strong force on the electrons, pulling them in closer. So even though there are more electrons in large atoms, they are pulled in closer, leaving the overall size of the heavy atoms the same as for light ones.

The following table lists the sizes of the most important atoms in this story. It is based upon The Nature of the Chemical Bond by Linus Pauling. The radius is given in nanometers. The figure represents the so-called Van der Waals radius, which is based on the distance atoms are held apart in a Van der Waals bond.

Carbon is a problem as the size changes depending on what atoms it is bonded to. In fact this applies to all atoms but it is worse for carbon since it can form 4 covalent bonds. Notice how the size goes up as we go through the atoms in the order HONC.

To get a feeling for how large atoms are, see the page on Atoms on Soccearth.