hoyo-hall-period 7

Aristotle (400 BC)

400

Aristotles theory states thal all matter is made up of fire, water, air and earth.He did not like the idea of the atom being the smallest component of matter

Democritus (450 BC)

450

Democritus theory stated that everything is physically made up of atoms.Also stated that atoms can never be broken down into pieces.His idea on what the atomic model looked like consisted of a clear sphere with no electrons or nucleus.He also stated that they all have different characteristics with things like size and shape. He had drawn this model demonstrating that atomscannot be destroyed.

John Dalton

Oct 25, 1803

He first advanced his theory in 1803. His theories stated that all matter consists of tiny particles and are indestructible and unchangeable.Also that elements are characterized by the mass of there atoms which proves when elements react there atoms combine and always come out to whole number ratios

Marie and Pierre Curie

Oct 25, 1896

In 1896 Marie & Pierre Curie discovered 2 new elements and did much research on radioactivity.During World War 1 Marie dedicated all her time in the development of the use of X rays in medicine.In 1903 she obtained her doctrate for a thesis in radioactive substances and won the Nobel Prize for physics.

Henri Becquerel

Oct 25, 1896

He studied the properties of the atom such as magnetism and radioactivity.He was successful in the study of radioactivity mostly. He experimented with with light and the absorption of crystals.He discovered a problem one day with uranium that projected the idea that uranium is radioactive

JJ Thompson

Oct 26, 1897

Thompson experimented with currents of electricity inside empty glass tubes. His observations led him to think that the light rays are streams of particles that are even much smaller than atoms. He called these particles corpuscles and proposed that they might be the make up of all the matter in atoms.

Ernest Rutherford

Oct 25, 1911

Ernest found that a narrow beam of alpha particles gets broader when it passes through a thin film of metal.He discovered that protons positively charge particles when he used his gold foil experiment. Also he discovered atoms are made of empty space.

James Chadwick

Oct 25, 1913

James proved the existance of the neutrons which resulted in the mass solution.This led to the investigation of the nature of the nucleus and its forces for the hidden mass in atoms.He was congradualated in 1935 for his excellence in physics.

Niels Bohr

Oct 26, 1922

He made foundational contributions to the understanding of the atomic structure. He recieved a nobel prize for his excellence.He developed the model of the atom with the nucleus at the center and electrons orbiting around it which he compared to the planets and the sun.

Rober Millikan

Oct 25, 1923

Robert Millikan was the person to discover the charge of a single electron.He made this discovery by using the Oil Drop Method.Also proving that the quantity was a constant for all electrons.The Oil Drop Method was proven accurate.