The main scientists that contributed to the discovery of the atom were Rutherford, Niels Bohr, J.J. Thompson, Dmitri Mendeleev, and John Dalton.

Rutherford is well known for the experiment that he performed which was called the Gold Foil Experiment.

Niels Bohr described that all electrons rotated around the nucleus of an atom. He also made the Bohr Atomic Model which said that atoms take in and give out radiation when electrons jump between allowed or stationary states.

J.J. Thompson discovered the electron and used the model of someone stirring pudding with chocolate chips in as an example of an atom.

Dmitri Mendeleev was the one who came up with the organization of periodic table.

John Dalton was the scientist who came up with 5 theories about the atom which were:

• All atoms of a given element are identical.
• Elements are composed of atoms.
• Atoms of different elements can be distinguished from one another by their relative weights.
• Atoms can combine to form a compound.
• Atoms can neither be created nor destroyed, but divided into smaller particles.

John Dalton was the earliest scientist to make a theory about the atom, and that was in the year of 1803.

Dmitri Mendeleev was the second scientist to make his theory, and that was in 1869.

J.J. Thompson was the third scientist that made is theory, and this was in the year of 1898.

Rutherford was the fourth scientist to make a theory, and this was in the year of 1911.

The last scientist to make his theory about the atom was Niels Bohr in 1913.

As you can see there was a pretty good length between all these theories of the atom. During this early time the equipment they hade wasn't very advanced making their work not exactly correct all the time.

It’s important that we know the structure of the atom because understanding the characteristics of atoms gives us information of how they are classified with other elements.