Question: what is a atem

Andrew Cairns answered on 16 Nov 2011:

An atom is the smallest part of an element that still can be defined as being that element. An element is a pure substance that only has one type of atom in it.

These definitions are slightly difficult because it seems circular – basically all the elements are in the periodic table. Each different element has atoms; these made up of different numbers of protons, neutrons and electrons. The protons, neutrons and electrons are the same in every atom in the world and so do not define the element.

So:

Protons + Neutrons + Electrons = Atom of a specific element
Many atoms of the same type = element
Atoms of different types bonded together = compound

‘Atom’ means “indivisible” as it was originally thought that the atom could not be divided into anything smaller. Then we did some experiments and worked out that it can be!