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330
Four elements theory
Aristotle proposes the four element theory that any visible object is made up of either air, water, fire or earth. -
440
Development of the atom
Greek philosophers, Leucippus and Democritus developed the idea of atoms, that all particles are made up of matter. -
Development of the atom
Isaac Newton propsed a mechanical universe with small solid masses in motion. -
First list of elements
Antoine Lavoisier constructed the first list of 33 elements, distinguishing between metals and non-met -
Dalton's Law
John Dalton proposed ‘Dalton’s Law’ stating that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. -
Development of the atom
Jakob Berzellus developed a table of atomic weights for the elements and introduced letters to symbolize them. -
Development of the pereodic table
John Newlands an English chemist proposed the law of octaves which stated that elements repeated their chemical properties every eighth element. -
Development of periodic table
JJ Thompson discovered the electrons, using properties of cathode rays. -
Development of the atom
Ernest Rutherford established that the nuclear charge on a nucleus was proportional to the atomic weight of the element. -
Developement of the Atomic number
Henry Moseley determined the atomic number of each element and modified the periodic law. -
Development of the atomic model
Niels Bohr developed the Bohr atomic model, with electrons travelling in orbits around the nucleus and chemical properties determined by how many electrons are in the outer orbit. -
development of the atomic structure
Niels Bohr developed an explanation of atomic structure, and built a an atomic model that had atoms make up of successive orbital shells of electrons. -
Development of the neutron
James Chadwick using alpha particles discovered a neutral atomic particles with a mass close to a proton and so the neutron was made. -
Development of the atom
John Newlands arranged the elements in order of atomic weight, observing the similarities of the elements. -
Development of the periodic table
Dimtri Mendeleev started the development of the periodic table arranged the elements by atomic weight and properties. The table contained 17 columns with two periods of seven elements.
