The Atom Theroy

Timeline

Ancient Greek Model

In 400 B.C the philosopher Democritus thought that matter could not be divided inde finitely. His idea was that you could cut an object in half many times but eventually you would get down to a small particles that could no be divided. He called called these particals atoms. Even though Aristotle theory was wrong incorrect, it was accepted as truth for nearly 2000 years.

Dalton Model

From the ancient Greek times unit the 1800s, the world thought of atoms in the same way.Most people hadn't even heard of the word atom before . In 1803 , John Dalton theorized that an atom was like a tiny spheres. Dalton also revolutionized atomic theory by saying that in a chemical reaction , none of atoms disappear , and they are just rearranged in different orders.

Thompson model

In 1897 ,Joseph Thompson proposed that atoms were spheres of positive electricity that had little pieces of negative electricity floating around inside of them. This was a major discovery because he was the first to conclude that there are particals smaller than a atom.

Rutherford Model

Ernest Rutherford took a giant leap in figuring out what we think atoms look like today. Before , all atom models were either blocky or just spheres with pieces of the atom closed inside like a box.But his model did not include the yet discovered protons and neutrons.

Bohr Model

Niels Bohr was a Danish scientist who introduced the most commonly know model of an atom in 1913. His model consists of a central nucleus (composed of protons and neutrons.)

Broglie and Schrodinger Model

In the 1920s Brogie and Schrodinger developed the electron cloud model.They theorized that the Bohr model was incomplete , and that the electrons do not orbit around like planets. Insted they proposed that the electrons existed in clouds around the outside of the dense nucleus (which contained protons and neutrons).