History of Atomic Theory

Democritus

400

born (460 BC) in the ancient Greek city of Abrade. and his theory, the universe and all matter obeyed these principles: 1. Everything is composed of atoms, physically but not geometrically, invisible. 2. Between atoms is empty space. 3. Atoms= indestructible. 4. Atoms will always be in motion. 5. There are infinite numbers that differ in shapes and sizes....he used analogies from sense experiences, he gave a picture or image of an atom that distinguish them and was always cheerful at work.

John Dalton

1803

in Manchester ,born 1766, he was best known for pioneering. Proved mass was all created by atoms. His experiments on gases did this discovery. (proposed the 1st evidence based atomic theory) This principle eventually became known as Dalton's Law of Partial Pressures. His parts to the atomic theory is everything is composed of atoms which are building blocks of matter (unbreakable). atoms of an element are identical. The atoms of different elements vary in size.

J.J. Thomson-

1897

In Cheetham Hill, England he Discovered the electron.
while Experimenting with cathode ray, tube(which looked at the negative charges) then
He was awarded the Nobel Prize in physics in 1906 for the discovery of the electron (born 12-18-1856)

Robert Millikan

1909

American Physicist ,born March 22, 1868, who discovered the electron charge using a series of experiments, one like the Oil drop. Where he dropped oil drops instead of water between two metal electrodes by balancing downward gravitational force... to determine the charge of the electrons. Later on, he won a Noble Prize because of this.

Earnest Rutherford

1911

Born, august 31, 1871. He Contributed with Gold Foil experiment, where he shot minute particles at a sheet of gold to see where they deflected and demonstrated the atom holds a nucleus. He created the Rutherford Model to prove the discovery. And later realized atoms were indestructible. To realize, he designed the experiment using radioactive probes to see the structure. During this time he lived in Canada and in a different time, England.

Neils Bohr

1913

Born, Oct. 1885. He Made a model of the atom that has a small, positively charged nucleus surrounded by orbiting electrons. He proved there was orbiting electrons which determines the element. He lived in Copenhagen and his father won noble peace prizes.

Erwin Schrodinger

1926

born on 1887, Erdberg, Vienna Austria... b.he discovered a wave of equation for movements. ….c. used mathematical equations to describe the likelihood of finding an electron in a certain position…. D. he was referred to the father of quantum physics…… e. Quantum mechanical model.

James Chadwick-

1932

born 1891 in Manchester...discovered atoms had neutrons. Chadwick in 1932 bombarded beryllium atoms with alpha particles, therefore an unknown radiation was produced. And the interpretation was that this radiation was being composed of particles with a neutral electric charge which became known as a neutron. Then received Nobel Prize for Physics in 1935 for the discovery of the neutron. (name if the model was quantum mechanical model of the atom).