Atomic Theory

Democritus

460

Democrritius discovered the atom.

Antoine Lavoisier

Aug 26, 1743

Discovered the rule of oxygen plays in combustion. Recognized and named oxygen in 1778 and hydrogen in 1783. He also helped construct the metric system.

Joseph Louis Proust

Sep 26, 1754

Helped prove the idea that every pure chemical compund consists of elements ina a definite proportion. Proposed the law of constant composition in 1799.

John Dalton

Sep 6, 1766

Proposed the law of mulitple proportions. This law led ro the atomic theory in 1803. He also developed the concept of the mole and proposed a system of symbols to represent atoms of different elements.

Michael Faraday

Sep 22, 1791

Declared laws of electrolysis/not praponet of atomism. The laws were: The amount of chemical change or decomposition is exactly proportional to the quantity of electricity that passes in the solution and the amounts of differemt substances deposited or disolved bt the same wuantity of electricity are proportional to their chemical equivalent wights.

Henri Becquerel

Dec 15, 1852

KNown for the discovery of radio activity.

J.J.Thomson

Dec 18, 1856

He identified the negitivly charged electron in 1897.

Max Planck

Apr 23, 1858

Used the idea (discetete units of energy) to explain hot glowing matter. Discovered quantum theory. It revolutionized the understanding of the atomic and subatomic process.

Ernest Rutherford

Aug 30, 1861

Proposed the nuclear atom. He also proposed that all of the positive charged and all of the mass of the atom occupied a small volume at the center of the atom. HE also proposed the existence of the 3rd atomic particle, the nuetron.

Robert Milikan

Mar 22, 1868

Determined the unit charge of ther electron in 1909 thus following the calculation of the mass of the electron and the positivley charged atoms.
e=1.60*10^-19

Lisa Meitner

Nov 7, 1878

Conducted experiments veryfying that heavy elements capture neutrons and form unstable products which undergo fission. Gave yth first theoretical explanation of fission.

Otto Hahn

Mar 8, 1879

Recognized that the uranium atom which bombarded by neutrons, actually split. Helped by lisa Meither and Fritz Strassman. Discovered nuclear fusion.

Albert Einstein

Mar 14, 1879

Discovered the theory of relativity. Published the equation e=mc^2

Niels Bohr

Oct 7, 1885

Contributed to quantum theory and his research in the structure of atoms. Was the first to discover that electrons travel in separate orbits. Created the atomic model. The element Bh is named after him.

Ernest Schrodinger

Aug 12, 1887

Well known for the Schrodinger equation. This equation is the wave equation of a non reletivistic quantum mechanics.

James Chadwick

Oct 20, 1891

Discovered the nuetron in 1932. His discoverey of the nuetron led to the discovery of fission and ulimatley the atomic bomb.

Louis DeBroglie

Aug 15, 1892

Developed the wave mechanics theory.

Marie & Pierre Curie

Jan 1, 1896

They discovered radioactivity.

Glen T. Seaborg

Apr 19, 1912

Identified six transuranium elements and suggested a change in the layout of the periodic table.

Aristotle

Mar 2, 2022

He discovered that the earth was round. He also believed in the four elements: earth, fire, air, water.