-
400
Aristotle Atomic Theory
(NOTE:This is 400 B.C)
Aristotle believes all things are made of fire, air, earth, and water. There were two forces, conflict and harmony. He also believed there was a fifth element aither which made up the heavens. -
460
Democritus Discovers Atoms
(NOTE: This is 460B.C.)
Democritus claimed everything is made up of basic matter particles called atoms, or atomos on Greek. -
John Dalton's Atomic Theory
John Dalton studied and experimented with elements to create his atomic theory:
-All matter is made of atoms. Atoms are indivisible and indestructible.
-All atoms of a given element are identical in mass and properties
-Compounds are formed by a combination of two or more different kinds of atoms.
-A chemical reaction is a rearrangement of atoms. -
Döbereiner's Discoverys
Döbereiner discovered trends of certain properties in groups of elememnts -
J.A.R. Newland's Contribution
Newlands was the first person to arrange the periodic table of elements by their atomic weights -
Dimitri Mendeleev Creates First Periodic Table
Mendeleev created the first periodic table with the 63 known elements arranged by atomic mass and properties. He even correctly predicted two yet to be discovered elements. -
Lothar Meyer's Contribution
He noticed that when the elements are arranged in the order of their atomic weights they fall into groups that share similar chemical and physical properties. He also made a plot comparing atomic volume and weight. -
William Crookes' Contribution
Crooke developed the Crooke's tube. From that, he later developed the cathode ray tube that used a stream of free electrons. -
Max Planck and His Constant
Planck discovered the quantum of action, (Planck's constant h) explaining the pattern of light intensity emitted from a black body at any given frequency -
Henri Becquerel's Discovery
Becquerel discovered x-ray like radiation from some phosphorescent materials when illuminated by sunlight. This is known today as radiation -
J. J. Thomson's Atomic Model
This is the "plum pudding" atomic model J.J.Thomson proposed after discovering the electron -
Rutherford's Atomic Theory
Rutherford discovered, by firing radioactive particles through gold foil, that atoms have a centeral positive nucleus with negativley charged electrons orbiting the nucleus. -
Neils Bohr's Atomic Model
Bohr establishes that electrons travel in stationary orbits, this led to the calculation of energy levels and the development of the solar system atomic model. -
Schrödinger and Quantum Mechanics
Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This is known as quantum mechanics. -
The First Successful Cloning
Dolly the sheep, the first the first mammal to be successfully cloned from an adult cell, is born.
