Atoms are the building blocks of all matter. Atoms are very small and cannot be seen by the human eye or even with microscopes.
An atom is made up of protons, neutrons and electrons. Protons have a positive charge and are found in the atom's nucleus. Electrons have a negative charge and orbit around the nucleus. The protons' positive charge is balanced by the negative charge of the electrons while a neutron has no electrical charge. Different atoms have different numbers of these subatomic particles, the atoms have different properties, and they are classified into 'elements'. The list of all the known elements, their relationships, and their chemical symbols, is known as the periodic table.
Atoms bond together into stable groups of atoms called 'molecules'. Molecules can be composed of atoms from the same element, or they can be a compound of atoms from two or more different elements. For instance, a molecule of water contains two hydrogen atoms and one oxygen atom – hence the symbolic formula for water is H2O.
