AQUINO, Melchizedek




500 B.C.E

A Greek Philosopher who develop the Theory of Atomism, the concept of everything is composed of stoms


430 B.C.E

Proposed an Atomic Theory (along with his mentor Leucippus) which states that all atoms are small, hard, indivisible and indestructible particles made of a single material formed into different shapes and sizes. He called it "Atomos"

John Dalton


Proposed an Atomic Theory which states: First, all matter is made up of tiny indivisible and indestructible atoms. Second, atoms of the same element are the same. Third, atoms of different elements are different. And finally, atoms combine in whole number ratios to form compounds.

J.J. Thomson


Used cathode rays to discover the electron. Measured the bending of the rays to determne the charge to mass ratio of the electron, modified cathode ray tubes were used to discover the positively charged proton

Albert Einstein


Photoelectric Effect: when light of a certain frequency shines on a metal, electrons are emitted.

Ernest Rutherford


Studied substances, especially alpha particles. Conducted the gold-foil experiment, which determined that the atom is mostly empty space, with a very small, positive nucleus.

Niels Bohr


improved upon the atomic model by trying to answer the question: why aren't electrons pulled into the nucleus?

electrons travel in definite energy levels without radiating energy; electrons in each orbit have a certain amount of energy; energy increases as distance from nucleus increases; electrons lose energy by dropping energy levels

Victor de Broglie


He developed his Theory of electron waves which described the behavior and properties of an object that varies in time or space.

Erwin Schrodinger


Schrodinger's Wave Equation
-treat the electron like a wave
-developed an equation used to determine the probability of finding the electron in any given place around the nucleus
-solutions to the equation are quantum numbers

Werner Heseinberg


Heisenberg published his Uncertainty Principle, which states that it is impossible to know the exact location and velocity of a particle at a given time.

James Chadwick


Discovered the existence of neutrons.

Otto Hahn, Lise Meitner and Fritz Strassmann


They discover Uranium fission.