History of the atom
An atom is said to be particle of matter and it can exist alone or in other combinations. Although throughout history there have been some theories regarding atoms it was only in 1808 Physicist John Dalton through his experiments and thesis explained the nature of chemical bonds and chemical compounds.
In his experiments he demonstrated how atoms linked together to form molecules. Evolving from this to the modern day it is known that for every atom there is a nucleus where electrons orbit around it. This nucleus is more than 99.9 percent of the atom. So in comparison the electrons are very small in size to the nucleus.
Within the nucleus consists of protons which has a positive charge and a neutron which as a negative charge.
The number of the protons within the nucleus is the atomic number of an element. These chemical elements are used in modern science, for example the first 2 elements are Hydrogen and Helium with the first having 1 proton and the second 2.