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450
Democritus
450 BCE
Theory revolves around the atoms that are present in the atmosphere. These are about the atoms that are present in all the forms of existence; for instance, solid or liquid. -
Lavoisier
Lavoisier clarified the concept of an element as a simple substance that could not be broken down by any known method of chemical analysis, and he devised a theory of the formation of chemical compounds from elements. -
Dalton
Dalton's Atomic Theory 1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms. -
Maxwell
Thus there was never an explanation of how the 'particles' generated these 'Electric and Magnetic Forces', and how these forces acted on other particles. And given consideration you begin to realise that Faraday's Force Fields were only ever mathematical constructions, and ultimately they must have a cause. -
Thompson
proposed a model of atom which is known as plum pudding model or Christmas pudding or chocolate chip cookie model. -
curie
Studied and identified radioactive elements -
Planck
the idea that energy is emitted in discrete quanta, contrary to classical physical theory. -
Milikan
Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and found the mass (m = 9.11 x 10 -28 gram) of an electron -
Rutherford
He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus. -
Moseley
Using x-ray tubes, determined the charges on the nuclei of most atoms. He wrote"The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganize the periodic table based upon atomic number instead of atomic mass. -
Bohr
His atomic model had atoms built up of sucessive orbital shells of electrons. -
Heisenburg
This is believed to be the way a particle escapes the charge (forbidden potential well) at the nucleus of an atom and is the mechanics of radioactive decay. -
Schrodinger
Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom. -
Chadwick
discovered the neutron -
Aristotle
He believed in the four elements of air, earth, water and fire.
384-322 BC
