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470 BCE
Democritus
Democritus was a Ancient Greek philosopher who was remembered for his formulation of and atomic theory. But in 460 BC he performed a very simple experiment. He took a seashell and broke it up until it was a pounder and he couldn't break it anymore. He knew that everything could fit together, but could also be broken down into tiny parts called atoms. This discovery fed many other scientists to learn and discover more! -
Dalton
John Dalton was a English Chemist who was also known for his theory of the atom. There are four parts to his theory... 1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties. 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms. He found out many things about atoms by experimenting with gas and evaporation. -
Thompson
J.J Thompson was a English physicist. In 1897, Thompson discovered that electrons have a negative charge. He discovered this by his Cathode experiment, where he demonstrated that cathode rays were negative. He also used gases to find positively charged particles. -
Rutherford
Ernest Rutherford was a New Zealand physicist who came to be known as the father of nuclear physics. His biggest experiment was his gold foil experiment. He simply used alpha particles sent out by radioactive elements to serve as probes to see how the atomic structure worked. This helped and led other great scientists to learn and add on to the atomic theory. -
Bohr
Niels Bohr came up with a atomic theory for the hyrdogen atom based on a theory known as the quantum theory. We see how this theory works in Bohr models, used to better show what each element consists of. It shows how protons, neutrons, and electrons are arranged. It helps students in school in today's world to learn better about the periodic table.
