The Online Library of Knowledge



Atoms are shown here as coloured balls.Atoms are shown here as coloured balls. All matter is made of atoms. An individual atom is far too small to see other than with the most powerful microscopes. But atoms joined together make up every solid object, substance, chemical and material in the Universe. A pinhead, for example, contains about one billion billion atoms. Atoms themselves are not solid, like marbles, but mostly empty space. But this space contains even smaller pieces of matter known as subatomic particles. There are three main kinds: protons, neutrons and electrons. The protons and neutrons are gathered together in the middle of the atom, forming its central part or nucleus.

Inside an atom, electrons orbit the nucleus.Inside an atom, electrons orbit the nucleus.


Electrons are much smaller than protons and neutrons. Minuscule bundles of energy, they whizz around the nucleus at the speed of light. Electrons do not move at random, however, but, in normal circumstances stay in certain layers known as shells. The number of shells an atom has depends on the number of electrons it contains. A carbon atom, for example, has six electrons in two shells. It is the presence of electrons that make the atom behave like a solid, in the same way that a fan blade spinning rapidly looks and behaves as if it were solid.

Inside an atom, there are the same number of electrons as there are protons. Both have electrical charges: electrons negative, protons positive (neutrons have no charge at all). Unlike charges attract, so the atom is held together. The two sets of opposite charges balance each other out so the whole atom has no charge. This makes it stable or unlikely to break up.

A hydrogen atom is about one ten millionth of a millimetre across. Its nucleus is 100,000 times smaller than the whole atom.

© 2020 Q-files Ltd. All rights reserved. Switch to Mobile