Atoms are the smallest part of an element which still has all the properties of that element. Atoms of different elements have different properties to each other and this is due to their structure.
Atoms have three common components to them. They have protons, neutrons and electrons.
These three subatomic particles, and how many of them there are, affect how the atom behaves.
Protons have a positive or +1 charge. They also have an atomic mass of 1.
Neutrons are neutral. They have no charge at all. Neutrons also have an atomic mass of 1.
Electrons have a negative charge or -1 charge. Electrons are said to have negligible mass, we treat them as if they have no mass at all.
Protons and electrons have opposite charges and when there are equal numbers of both the atom is said to be neutral, for example sodium has 11 protons and 11 electrons.
The subatomic particles are found in one of two places in the atom. Protons and neutrons are found in the nucleus of the atom.
This is a very small condensed area at the centre of the atom. Since only protons and neutrons are found in the nucleus, this means that the nucleus of the atom has a positive charge.
Electrons orbit the nucleus in shells. The negative charge of the electrons in the shells cancels out the positive charge of the protons, provided there are the same number of both.