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1891 - 1974
1871 - 1937
1856 - 1940
1791 - 1867
1754 - 1826
460 - 370 BC
1926 - Today
Faraday studied the effect of electricity on solutions and came up with the term "electrolysis" as a splitting of molecules with electricity. In addition, he coined the term "ion".
He developed laws of electrolysis.
He did a few experiments and discovered the possibility of the existence of negatively charged particles called "electrons" within the atom.
Proust published the Law of Definite Proportions in 1799 which states that a compound is composed of exact proportions of elements by mass, no matter how the compound was created. So, according to his law, every pure chemical compound consists of elements in a definite proportion. This law is currently valid as well.
James Chadwick discovered neutrons in 1932. He went onto measuring their mass.
Democritus was a Greek philosopher that said all matter was made up of indivisible particles called "atomos".
He also said that;
J. J. Thomson discovered the existence of electrons in 1897. He also measured the ratio of the charge of electron.
He is famous for his "Plum Pudding Model"(1904) that symbolizes his idea of an atom. The plums in the pudding represent the electrons which he believed were randomly spread in an atom. The pudding represents a positively charged cloud. However, this was a hypothesis therefore was not based on any experimental evidence, and is an incorrect theory.
Rutherford proved Thomson's atomic model wrong by testing it with the gold foil experiment in 1911.
He discovered protons in 1919.
Gold Foil (Alpha-Scattering Experiment):
He shot alpha particles at a thin sheet of gold foil in order to observe how the particles scatter.
His results were;
The conclusion he reached was;
De Broglie, Heisenberg, Schrödinger reached the conclusion that we are unable to detect the exact place of electrons and their orbits and we can only calculate the probability of finding the electron around nucleus, which is the electron cloud model.
These scientists said that electrons exist only in certain discrete energy levels which are described by quantum numbers.
Heisenberg
De Broglie
Schrödinger
Robert Millikan determined the electric charge of electrons between 1908 and 1917.
Dalton claimed that all atoms are indivisible and indestructible, just like Democritus had in the past.
He created the "Billiard Ball Model".
He also postulated that;
Lavoisier created the Law of Conservation of Mass which states that matter is neither created or destroyed and mass always remains the same during chemical reactions. This law is still applicable to today's world of chemistry.
He also found out that;
Bohr changed Rutherford's model by stating that electrons cannot move freely around the nucleus.
He said that electrons move in circular orbits around the nucleus. These orbits have specific energy levels and are all placed in a different distance from the nucleus. They are also called as shells.
Moreover, Bohr explained the Hydrogen Emission Spectrum. He wasn't able to explain the atomic spectrum of other elements.
Bohr's model said that electrons are subatomic particles and have very small mass but very high velocity.
In 1894, Stoney said that electricity was made of negatively charged particles called "electrons."
1868 - 1953
1855 - 1962
1826 - 1911
1766 - 1844
1743 - 1794