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460 BCE
Democritus
Democritus was an Ancient Greek pre-Socratic philosopher from Abdera, primarily remembered today for his formulation of an atomic theory. -
429 BCE
Plato
Plato was an ancient Greek philosopher born in Athens during the Classical period -
384 BCE
Aristotle
Aristotle was an Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy -
Robert Boyle
Robert Boyle was an Anglo irish natural philosopher, chemist, physicist, alchemist and inventor. Boyle is largely regarded today as the first modern chemist -
Robert Millikan
Robert Andrews Millikan was an American experimental physicist who won the Nobel Prize for Physics in 1923 for the measurement of the elementary electric charge -
John Dalton
John Dalton FRS was an English chemist, physicist and meteorologist. He is best known for introducing the atomic theory into chemistry. -
Mendeleev's Pd Table
Dmitri Ivanovich Mendeleev was a Russian chemist and inventor. He is best known for formulating the Periodic Law and creating a version of the periodic table of elements. -
Newland's Law of Octaves
John Newlands attempted the 62 elements known at that time. He arranged them in an ascending order based on their atomic masses and observed that every 8th element had similar properties. -
Photelectric Effect
1887 by the German physicist Heinrich Rudolf Hertz. In connection with work on radio waves, Hertz observed that, when ultraviolet light shines on two metal electrodes with a voltage applied across them. -
Discovery of Radioactivity
By accident, he discovered that uranium salts spontaneously emit a penetrating radiation that can be registered on a photographic plate. -
Planck's Quantum Theory of Light
Planck proposed that the energy of light is proportional to frequency, and Planck's constant, is the constant that relates them. -
Plum pudding model
Thomson's plum pudding model of the atom, the electrons were embedded in a uniform sphere of positive charge, like blueberries stuck into a muffin. -
Rutherford's gold foil experiment
A piece of gold foil was hit with alpha particles, which have a positive charge. Most alpha particles went right through. This showed that the gold atoms were mostly empty space. -
Bohr's Planetary Model
Bohr model, description of the structure of atoms, and hydrogen. -
Mosley's Atomic Number's
Moseley published a paper in which he concluded that the atomic number is the number of positive charges in the atomic nucleus. -
Discovery of the proton
The discovery of the proton is credited to Ernest Rutherford, who proved that the nucleus of the hydrogen atom. -
Schrodinger Equation
The Schrödinger equation is a linear partial differential equation that governs the wave function of a quantum-mechanical system -
Heisenberg Uncertainty Principle
a fundamental concept in quantum mechanics. It states that there is a limit to the precision with which certain pairs of physical properties -
Discovery Of Neutron
James Chadwick conducted an experiment in which he bombarded Beryllium with alpha particles from the natural radioactive decay. -
The Alchemists
The alchemists believed that all metals were formed from two principles — mercury and sulfur.