The Atom Theroy
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.
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.
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).