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He discovered atom around 400 B.C.E . , He was an greek philosopher that thought that all matter is composed of indivisible elements -
He established the law of conservation of mass, determined that combustion and respiration are caused by chemical reactions with what he named “oxygen,”
Between 1772 and 1794 -
The total pressure of a mixture of gases amounted to the sum of the partial pressures that each individual gas exerted while occupying the same space. In 1803 -
In 1886 he discovered what he termed Kanalstrahlen, or canal rays, also called positive rays; these are positively charged ions that are accelerated toward and through a perforated cathode in an evacuated tube. -
Discovered xrays in 1896.. -
On April 30, 1897, British physicist J.J. Thomson announced his discovery that atoms were made up of smaller components -
He discovered radon in 1900 , radon was an radioactive element
He found that the atom consists mostly of empty space, with its mass concentrated in a central positively charged nucleus -
Max Planck was a German theoretical physicist who discovered the quantum of action, now known as Planck's constant, h, in 1900 -
In 1910 Robert Millikan succeeded in precisely determining the magnitude of the electron's charge. -
a model of the atom in which the electron was able to occupy only certain orbits around the nucleus. In 1913 -
1924 Louis de Broglie introduced the idea that particles, such as electrons, could be described not only as particles but also as waves. -
Erwin Shrodinger described how electrons move in wave form, and developed the Schrodinger equation which describes how the quantum state of a system changes with time. He discovered in 1926 -
In february 1927 , Werner heisnberg developed a key piece of quantum theory -
discovery of the neutron in 1932.