Chapter 2 - Distances

Units of measurement

Before I start telling you about distance, I should point out that atoms and molecules are incredibly tiny. For example, if you owned a magical machine that could expand any object, and you put me in your machine and blew me up until my head touched the Moon, my carbon atoms would only be about the size of ping-pong balls.

Atoms are so small, in fact, that scientists have invented a special tiny unit of distance, the Ångstrom (Å), to describe atoms. 1 Å is defined as10–10 m and a typical atomic radius lies between 1-2 Å.

Since an Ångstrom is defined in metric units, it can also be converted into other standard metric distances:

1 Å = 10–10 m

1 Å = 10–8 cm

1 Å = 0.1 nm (nm = “nanometer” or 10–9 m)

1 Å = 100 pm (pm = “picometer” or 10–12 m)

In recent years, scientists in Europe have taken to using picometers (pm) in place of Ångstrom. If you read a book or article by these chemists, you’ll find distances reported in pm, and typical atomic radii will fall between 100-200 pm.