-
370 BCE
Democritus
one of the two founders of ancient atomist theory -
348 BCE
Plato
Greek philosopher in Athens, Greece. He founded Platonist school of thought and the Academy, the first institution of higher learning in Europe. -
322 BCE
Aristotle
Taught by Plato, he was the founder of the Peripatetic school of philosophy. -
Lavoisier
He is most noted for his discovery of the role oxygen plays in combustion. He recognized and named oxygen (1778) and hydrogen (1783) -
The Alchemists
The alchemists believed that all metals were formed from two principles: mercury and sulfur. The mercury, with its properties of fluidity and fusibility, gave rise to the malleability of metals. The sulphur, with its essential property of combustibility, contributed weight and rusting -
John Dalton
Dalton's atomic theory suggested that all matter was comprised of indivisible and indestructible atoms with distinct masses and properties, and the organization determined the physical properties of the atom -
Newland's Law of Octaves
Generalization made by J.A.R Newlands stating that if atoms are organized according to increasing atomic weight, atoms with similar physical and chemical properties will be every 1st and 8th atom in that order. -
Mendeleev's Pd. Table
Mendeleev arranged the elements in order of increasing weight and broke them into rows such that elements in each column shared valence -
Photoelectric Effect
electrically charged particles are released from a material when it absorbs electromagnetic radiation. -
Discovery of Radioactivity
French physicist Henri Becquerel discovered radioactivity while studying early x-ray photos. -
Discovery of the Electron
During the 1880s and 1990s scientists, scientists studied cathode rays to see what was carrying electrical properties in matter. The work of these scientists greatly assisted the discovery of the electron by English physicist J.J. Thomson. -
Planck's Quantum Thoery of Light
light bulb filaments should be heated to a temperature of about 3,200 Kelvin to ensure that most of the energy is emitted as visible waves -
Plum Pudding Model
The plum pudding model, also known as Thomson's plum pudding model, is an atomic model in which negatively charged electrons are encapsulated by positively charged neutro -
Rutherford's Gold Foil Experiment
Gold foil was hit with a positive particle, and it went right through, proving that gold atoms are mostly empty space -
Bohr's Planetary Model
A model of the atom, often called Bohr's Planetary Model because a set of electrons orbit the nucleus, similar to how planets orbit the sun. -
Mosley's Atomic Numbers
Moseley published a study in which he stated that the atomic number is the number of positive charges in the atomic nucleus -
Discovery of the proton
A proton is a positively charged particle in the nucleus of an atom discovered by Ernest Rutherford. -
charge of the electron
1.602176634 × 10−19 coulomb, which is considered the basic unit of electric charge. The rest mass of the electron is 9.1093837015 × 10−31 kg, which is only 1/1,836the mass of a proton -
Schrodinger's Equation
equation that governs the wave function of a quantum-mechanical system -
Heisenberg's Uncertainty Principle
Heisenburg discovered that the more we know about either a particle's speed or position, the less we know about the other. -
Discovery of the Neutron
James Chadwick announced that the nucleus also contained a neutrally charged particle -
Robert Millikan
American physicist honored with the Nobel Prize for Physics in 1923 for the measurement of the elementary electric charge and for his work on the photoelectric effect.
discovered charge of the electron