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465 BCE
Democritus
Developed the first concept of the atom. -
Antoine Lavoisier
He discovered oxygen and discovered that it makes up 21% of the air. He also disapproved the Phlogiston Theory, which stated that when fire (combustion) happened, phlogiston was released into the air. He came up with the Law of Conservation of Mass in result of disapproving the theory. -
John Dalton
He was a chemist who developed the modern atomic theory that everything is made up of atoms. He envisioned atoms as tiny, solid balls. -
Dmitri Mendeleev
He arranged the periodic table differently than the original. He arranged all 63 elements based on their atomic mass. This turned out to be seven groups that all had similar properties. -
Eugene Goldstein
He discovered canal rays through many experiments with cathode rays. His experiments showed that the cathode rays would take electrons off of atoms and attract them to a positively charged electrode. He knew that there had to be another ray that traveled in the opposite direction, which was the canal ray. -
J.J Thomson
He was an English Nuclear Physicist who studied the nature of electric discharge in a high-vacuum cathode-ray tube. He also concluded that electrons are part of the atom. -
Max Planck
He was a German physicist who came up with the quantum theory of energy. This theory contributed a lot to understanding atomic and subatomic processes. -
Robert Millikan
He was an American physicist who determined the size of the charge on a single electron using The Millikan Oil Drop Experiment. -
Ernst Rutherford
He was a New Zealand physicist who discovered that the atom had a nucleus and was mostly empty space rather than a ball of evenly distributed particles. He did this through his gold-foil experiment where he found that the elements bounced off of the gold foil instead of going through it. Because they bounced back, he realized they had to be mostly empty space with a dense center called a nucleus. -
Henry Moseley
He was an English physicist who discovered the concept of the atomic number. He realized that an atom is defined by its number of protons which did not match the current periodic table, so he made a revised one with atomic numbers in it. -
Neils Bohr
A theoretical nuclear physicist who discovered the nucleus and development of an atomic model. He based his discoveries off of the quantum theory. -
Werner Heisenberg
He was a physicist that was best known for his published work on the theory of quantum mechanics. He discovered a way to formulate quantum mechanics into matrices. His theory eventually lead to the discovery of allotropic forms of hydrogen. -
Erwin Schrodinger
He was an Austrian physicist who took the Bohr model and revolutionized it. He used this model to develop equations that would describe the likelihood of finding electrons in certain positions. This model is known as the quantum mechanical model. -
James Chadwick
He was an English Nuclear Physicist who made the discovery of the neutron in 1932. He discovered and proved that the neutron had about the same mass as a proton.
