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The complete history of the Universe -- from the Big Bang to 200 my into the future

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History of the Universe eBook. 398 pages, 300 illustrations only $2.99

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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 arenít.

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.

Atom

Radius

Hydrogen

0.12nm

Oxygen

0.14nm

Nitrogen

0.15nm

Carbon

0.16nm

Sulphur

0.185nm

Phosphorus

0.19nm

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

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History of the Universe eBook. 398 pages, 300 illustrations only $2.99

eBook only $2.99
398 pages, 300 images

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