Atomic Theory

Empedocles

495 BCE

Suggested that all matter was divided into 4 elements, air, fire, water and earth. His theory was accepted by Aristotle, one of the most famous Greek philosophers

Democritus

460 BCE

Suggested that all matter was made up of extremely small, indivisible, indestructible pieces called "atomos". He said that there is empty space between atomos', and that there is an infinite number and kinds of atomos'.

Asharya Kanad

150 BCE

Asharya Kanad is believed to be the first person to theorize the idea of an indestructible, indivisible particle of matter. He thought of this by cutting a fruit into small pieces.

The Alchemists

1500

Alchemy was an ancient form of chemistry, it stemmed from greek and roman philosophy. Their main goal was to transform regular everyday metals into gold. They also were looking for the "philosophers stone" which was said to bring perfection to life. Through the test they did they also found several elements that are still in our periodic table today, such as Hennig Brandt and the phosphorus story.

John Dalton

1803

Dalton's theory says that all matter is composed of atoms, which are extremely small indestructible, indivisible building blocks. He said that atoms of a certain element were all the same, and that the atoms of different elements differ in size and mass

Marie Sklodowska Curie

1867

Marie Sklodowska Curie created her own experiment to test Uranium rays. She concluded that the waves remained constant, regardless of the condition or form of the uranium. She theorized that the waves were based on the atomic structure of the element.

Max planck

1897

Max Planck is known for creating the quantum theory. This theory allowed us to further our understanding atomic and subatomic process.

J.J thomson

1897

J.J Thomson is known for his work with cathode ray tubes. He showed that all atoms had negatively charged subatomic particles called electrons. He is also famous for his "plum pudding" atomic model, where electrons were embedded in a positively charged "soup"

Hantaro Nagaoka

1904

Hantaro Nagaoka proposed that the atom had a planetary shape. His theory was that electrons orbit around a positively charged center. His ideas were based off Saturn and its ring

Ernest Rutherford

1910

Ernest Rutherford said that the atom is mostly empty space. He also said that the electrons orbit in that empty space around a positively charged nucleus. Also known for the Bohr-Rutherford Diagram

Neils Bohr

1913

Neils Bohr was a physicist in the early 20th century. He is known for his atomic theory that electrons revolve around the center of the atom. The electrons are in defined circular orbits. He also discovered that when one electron jumped from one orbit to another one with a lower energy, a quantum light is emitted

Louis De Borglie

1924

Louis De Borglie suggested that electrons and all matter have wave properties. This is called the De Borglie hypothesis, and is the center of the theory of quantum mechanics.

Werner Heisenberg

1925

Werner Heisenburg's theory was that you cannot assign position a position in space to an electron, or track it in its orbital. He also said that we couldn't assume that Bohr diagram actually exists.

Wolfgang Pauli

1925

Wolfgang Pauli is famous fro his discovery of the Pauli exclusion principle. It says that no two electrons in an atom can be in the same state or configuration at the same time.

Erwin Schrodinger

1926

Erwin Schrodinger is known for taking the Bohr model a step further. Using mathematical equations he described the likelihood of finding an electron in a certain position. This is called the quantum mechanical model.

James Chadwick

1935

James Chadwick is famous for one of the biggest discoveries in science. He discovered the neutron.

Lise Meitner

1938

Lise Meitner was the scientist who discovered that nuclear fission can produce large amount of energy, thus having the possibility to create an atomic bomb. She is known as the mother of the atomic bomb.

Albert Einstein

1939

Albert Einstein is famous for his theory of relativity (E=MC2). But his biggest contributions to atomic theory lies in the creation of the atomic bomb.

Rosalind Franklin

1945

Rosalind Franklin made several discoveries about the molecular structure of coal and carbon. Which were used in nuclear power plants to create strong carbon fibers and slow reactions.

Robert J. Le Roy

1971

Dr. Le Roy's mostly studied forces within molecules. He used quantum mechanics an computer models to analyze the forces between atoms. He is also known for the Le Roy - Bernstein theory.

Richard Bader

1991

Richard Bader discovered that electron density is very important if you want to explain the behavior of atoms. He theorized that atoms do not actually have orbitals.

Ronald J. Gilespie

1991

Ronald J. Gilespie contributed to the innovation of science be creating the super-acid. It became widely used in organic and non-organic chemistry.