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Q & A: Space Between Atoms

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Q:
How much space is there between atoms in our body?
- Sasha
Manchester, NH USA
A:
Sasha, luckily for us, the atoms in our body are governed by the same laws as the atoms outside of our body, so perhaps your question could be more generally phrased, "How much space is there between atoms?"

We'll take that to mean the distance from one atom to the next. Except in a gas, there really isn't "empty" space between atoms, which is the other thing you might have been asking about.

For things in the body which are liquids or gases such as air in the lungs or the water in blood, the way to find the distance between each atom is to do figure out the density, or number of particles in each volume of the gas or liquid.  At room temperature and atmospheric pressure, the air takes up 0.0224 cubic meters for every mole (6.022 x 1023 particles) of gas.  That's about 4 x 10-26 m3 per particle.  If we assume this space around each atom to be a little sphere around said atom then the radius of the sphere would be around 2X10-9 meters,  so that's the typical space between particles in the gas.  This dwarfs any distance between bonds of atoms if the particles are molecules as will be seen later.

For liquids the same method can be applied.  Water is a good example and it has a density of 1000 kg per meter cubed.  Since the molar mass of water is 0.018 kg per mole this gives a density of 55,000 moles per meter cubed of water.  This works out to one particle per  about 3 x 10 -29 m3.  Using the assumption of little spheres as before give the spacing between the molecules at about 2X10-10 m, much smaller than in air.

Atoms form bonds in several different ways,  but they all have similar bond lengths.  Generally speaking the space between the nucleus of two bonded atoms is around 10-10 meters.  This is also called one ångström (Å). It's approximately the size of the electron cloud of a single atom.

-Mark (mods by mbw)

(published on 05/24/11)

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