History of atomic theory

Democritus

500

He was born in 460bc and died 370bc. Matter is made up of small particles which he called atoms. He used logical thinking.

John Dalton

Oct 11, 1766

All matter is composed of tiny particles called atoms. He studied the evaporation of water into the air and was able to understand that the process increased gas pressure.

JJ Thomson

Dec 7, 1856

Thomson identified the electron which carries a negative charge. They showed that different gases placed in the tubes gereated streams of particles and conducted current.

Ernest Rutherford

Jun 15, 1871

Ernest hypothesized that an atom must be made up of mostly empty space, alpha particles to pass through foil. He used high-speed lightwieght atoms called alpha particles to bombard very thin pieces of gold foil.

Albert Einstein

Mar 14, 1879

he discovered his special theory of relativity stemmed from an attempt to reconcile the law of mechanics with the laws of the electromagenetic field. Einstein always appeared to have clear view problems of physics and the determination to solve them. He had of his own and was able to visualize the main stages on the way to his goal.

Neils Bohr

Oct 10, 1885

He described electrons as moving around the nucleus in fixed orbits that have a set amount of energy. His info about hature emissin of light by heated objects to update his model.

James Chadwick

Jul 2, 1891

Finally solved the problem, he identified the third important subatomic particles, the neutron. He based on his work on earlier experiments by French physicists irene and frederic jolit