Atomic Theory Timeline

Scientists

John Dalton

1803

He created Dalton's Atomic Theory which said that all matter is composed of atoms, atoms cannot be made or destroyed,
all atoms of the same element are identical, different elements have different types of atoms, and a chemical reaction is a rearrangement of atoms. He also published Dalton's Law which stated total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture.

Eugen Goldstein

1886

He concluded tha in addition to the cathode rays that travel from the negatively charged cathode toward the positively charged anode, there is another ray that travels in the opposite direction, from the anode toward the cathode. Goldstein called these canal rays because they pass through the channels in the cathode.

J.J. Thomson

1897

Thomson proved that cathode rays were actually some speedily moving particles. After meausirng their speed and specific charge, he concluded that these "corpuscles" (electrons) were about 2000 times smaller in mass as compared to the hydrogen ion, the lightest-known atomic particle

Ernst Rutherford

1899

He discovered aplha and beta radiation.

Max Planck

December 14, 1900

Planck combined the formulas of Wien and Rayleigh to form Planck;s radiation formula. He presented a theoretical explanation involving quanta of energy. He also discovered/created Planck's constant.

Ernst Rutherford

1902

He co-discovered that radioactivity was a course of action in which atoms from one element disintegrated into atoms of a different element

Ernst Rutherford

1903

He named gamma radiation and discovered it is more powerful than beta and alpha radiation.

Albert Einstein

1905

Einstein created the theory of relaitivity, which laid the basis for the release of atomic theory. He also formulated the Special Theory of Relativity. He then established the law of mass through his famous formula E=mc2

Ernst Rutherford

1909

He helped carry out the Geiger-Marsden experiment which allowed him to understanf the nuclear nature of atoms

Robert Millikan

1910

Millikan’s earliest major success was the accurae determinaton of the charge carried by an electron using the “falling-drop method”. He also proved that this quantity was a constant for all electrons, which demonstrated the atomic structure of electricity.

Ernst Rutherford

1911

The Rutherford model of the atom explained that a small positive charged nucleus was orbited by electrons

Robert Millikan

1912 - 1915

Millikan verified Einsteins’s very important photoelectric equation experimentally, and made the first direct photoelectric determination of Planck’s constant.

Henry Moseley

1913

He discovered systematic relation between wavelength and atomic number which is called Moseley's Law. He also predicted a number of missing elements and their atomic numbers.

Neils Bohr

1913

Bohr completed his theory of atomic structure in 1913. He stated that electrons have set energy levels and created a realistic model. His atomic theory was a combination of Rutherford’s work and ideas of the atom, with Planck’s Quantum Theory. Bohr received the Nobel Prize in Physics for his research in the atomic structure in1922.

Ernst Rutherford

1919

He was the first person to transfer one element into another through a nuclear reaction.

Ernst Rutherford

1921

He gave his theory about the existence of neutrons.

Werner Heisenberg

1925

He formulated the quantum theory of ferromagnetism, the neutron-proton model of the nucleus, and the S-matrix theory in particle scattering. He also suggested the unified field theory a.k.a the "world formula". He is known for one of the earliest breakthroughs to quantum mechanics.

Erwin Schrodinger

1926

He is known for the tremendous discovery of the Schrodinger Wave Equation. The Schrodinger Equation is a wave equation in terms of the wavefunction that predicts logically and precisely the probability of events or outcome.

Louis deBroglie

1927

He thought about dual nature of light; the wave - particle duality. He suggested that matter might behaveina similar matter. He made the theory of electron waves, and resolved and offered an explanation to a question that was brought up by calculations of the motion of electrons within atoms.

James Chadwick

1932

Chadwick discovered the exsistence of the neutron and that it had 0.1 percent more mass than a proton. This was one of the most important scientific discoveries of the twentieth century. He received the Noble Prize for discovery in 1935.

Other Scientists

Joseph Priestly

1770

discovered oxygen, carbon monoxide, and nitrogen dioxide

Antoine Lavoisier

1786

Father of modern chemistry

Antoine Lavoisier

1789

Law of conservation of mass

Alssandro Volta

1797

Batteries

Alessandro Volta

1800

Electrochemical cell

Michael Faraday

1821

first electric discovery

Michael Faraday

1832 - 1833

discovered laws of electrochemistry

Alfred Nobel

1864

Dynamite, Nobel Prize

Louis Pasteur

1888

Pasteurization process

Henri Becquerel

May 18, 1896

radioactivity

Marie Curie

1898

radioactivity

Sir Frederick Banting

1921 - 1922

Isolated insulin

Philo Farnsworth

September 7, 1927

TV

Wallace Carothers

April 1930

Neoprene

Gugliemo Marconi

1932

Radio

Leo Szilard

1933

Nuclear chain reactions

Wallace Carothers

October 27, 1938

Nylon

Leo Szilard

1940

Atomic bomb

Kary Mullis

1984 - 1985

Polymerase chain reaction

Historical Events

Gutenburg printing press

1448

Discovery of the Americas

October 12, 1492

Reformation of the Catholic Church

1545

Galileo convicted of Heresy

1633

Declaration of Independence

July 4, 1776

Civil War

1861 - 1865

First transcontinental railroad in U.S.

1869

Assassination of Archduke Ferdinand

June 28, 1914

Bolshevik Revolution

1917

Treaty of Versailles

June 28, 1919

Bombing of Pearl Harbor

December 7, 1941

First Cellular Phone

1974

Initial concept for World Wide Web (Internet)

1990 - 2000