Development of Atomic Theory

Democratus

440

Greek philosopher who said that everything is made up of atoms.

John Dalton

Jan 1, 1803

Was English and came up with the first real atomic theory, which said that "All matter is made of atoms. Atoms are indivisible and indestructible. All atoms of a given element are identical in mass and properties Compounds are formed by a combination of two or more different kinds of atoms. And a chemical reaction is a rearrangement of atoms.”

Rydberg

Jan 1, 1890

-Johannes Rydberg, Swedish
-created Rydberg Constant

-physical contact that has to do with the science of spectroscopy, specifically the atomic spectra

Thomson

Jan 1, 1897

-Joseph John Thomson, English
-explorations on the properties of cathode rays → discovered electrons
-plum pudding model

Planck

Jan 1, 1900

-Max Karl Ernst Ludwig Planck, German
-oscillator could only emit energy in a discrete quanta
→ quantum theory : nobel prize in 1918

Albert Einstein

Jan 1, 1905

German who created the theory of relativity. Which was the metric theory of gravitation and laid the basis for atomic studies.

Millikan

Jan 1, 1910

-Robert Andrews Millikan, American
- "falling-drop method" - accurate determination of the charge carried by an electron
-demonstrated the atomic structure of electricity

Mosley

Jan 1, 1911

-Henry Gywn Jeffreys Mosley, English Physicist
-Mosely’s law - complete understanding of atomic number and positive and negative charges in the atom

Rutherford

Jan 1, 1911

-Ernest Rutherford, British, New Zealand
-made a new model of the atom
-discovered the electron cloud did not influence alpha particle scattering
- said Thomson’s “plum pudding model was incorrect”

Niels Bohr

Jan 1, 1911

He was born in Denmark. Said that electrons were and clouds and could jump from cloud to cloud, and light is released when they jump.

Louis De Broglie

Jan 1, 1924

French man who created the matter and wave-partial duality, which started wave mechanics. He came up with this idea after Einsteins discovery of photons, which moved on waves.

Pauli

Jan 1, 1925

-Wolfgang Pauli, Austrian
-Pauli exclusion principle -no two identical particles with half-integer spin may occupy the same quantum state at the same time

Friedrich Hund

Jan 1, 1925

German who discovered that there must be electrons in each level before they double up.

Werner Heisenberg

Jan 1, 1928

German who published the Uncertainty Principal which said that the more you know about the location of a particle, the less is known about the momentum.

James Chadwick

Jan 1, 1932

English man who discovered the neutron by smashing alpha particles into Beryllium, which released neutrons. This help explain the weight of atoms.

Schroedinger

Jan 1, 1933

• Erwin Rudolf Josef Alexander Schroedinger, German -one of the fathers of quantum mechanics -Schroedinger equation (nobel prize in 1933) -describes how the quantum state of a physical system changes in time -Schroedinger’s cat thought experiment - a thought experiment with a paradox