-
345 BCE
Aristotle
He did not believe in the atomic theory. He believed that all substances are made up of water, fire, earth, and air. He ended up teaching his beliefs which lead to people not believing in Democritus idea. -
320 BCE
Democritus
He suggested that all matter is made up of small tiny particles called atoms. -
John Dalton
He came up with the idea that stands today. That Atoms cannot be destroyed chemically but can be nucular. -
Antonie Lavosier
The first breakthrough in the study of chemical reactions resulted from the work of the French chemist Antoine Lavoisier. -
Joseph Proust
He first published his Law of Definite Proportions in 1794. This law states that a compound is composed of exact proportions of elements by mass regardless of how the compound was created. -
Amadeo Avagadro
Amadeo Avogadro proposed what is now known as Avogadro's Hypothesis. The hypothesis states that at the same temperature and pressure, equal volumes of gases contain the same number of molecules or atoms. -
Henri Becquerel
Henri Becquerel discovered radioactivity which was an early contribution to atomic theory. He discovered this phenomenon while experimenting with uranium and a photographic plate. -
J.J. Thomson
He teamed up with crookes and discovered the electron of the atom. They discovered this when they realized the cathode ray were negatively charged. -
Madame Curie
Discovered polonium and radium with her husband, Pierre Curie. -
William Crookes
He discovered the element Thallium. Which became the fundamentals of discovering atoms. -
Albert Einstein
Albert Einstein formulates Special Theory of Relativity. Einstein calculates how the movement of molecules in a liquid can cause the Brownian motion. -
Ernest Rutherford
He decided to change the look of the atom design made by thomson's, and create his own by with alpha particles. -
Robert Millikan
His most famous work was the creation of the oil drop experiment. Which his experiment discovered a negatively charged particle, and that particle was smaller than the hydrogen atom. -
Henry Moseley
He created a law called the Moseley's law which is designed to separate and organize the elements on a table. -
Niels Bohr
Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. -
Max Planck
He created the quantum theory and was awarded the nobel prize because of his contribution to chemistry. -
Werner Heisenberg
Werner Heisenberg contributed to the atomic theory by including quantum mechanics, the branch of mechanics, based on quantum theory, used for interpreting the behavior of elementary particles and atoms. -
Erwin Schrodinger
Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom. -
Louis deBroglie
He was awarded the nobel prize for his work in quantum theory, and his prediction on waves of nature for neutrons. -
James Chadwick
Chadwick used Rutherford's idea of alpha particles, and created a particle for radiation. That particle has a neutral charge and is the same mass as a proton. Which came to be what is known today as the neutron.