Question: what are atoms

Serena Corr answered on 24 Jun 2013:

Hi shanti22

An atom is the smallest basic unit that makes up matter and is the smallest particle of an element that can exist. It can be broken up into three main subatomic particles: neutrons (which are neutral, i.e. they have no charge), protons (which are positively charged) and electrons (which are negatively charged). Overall, atoms do not have a charge, so there must be the same number of electrons as there are protons.

Lets take nitrogen as an example. Nitrogen has the atomic number 7 in the periodic table of the elements. That means that it has 7 electrons and 7 protons. If we want to find out how many neutrons it has, we subtract the atomic number from the mass number, which we can also find on the periodic table. The mass number of nitrogen is 14, so that means nitrogen must have a number of neutrons = 14 – 7 = 7 neutrons.