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Period: 460 BCE to 322 BCE
Democritus
The theory of Democritus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms, there lies empty space; that atoms are indestructible, and have always been and always will be in motion; that there is an infinite number of atoms and of kinds of atoms, which differ in shape and size. -
Period: 384 BCE to 322 BCE
Aristotle
Aristotle disagreed completely with the idea of Democritus and he said that the matter was made mostly by 4 elements air, water, fire, earth. -
Period: to
Lavoisier
Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. In other words, the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction. -
Period: to
Dalton
Independence of Mexico. And he showed that common substances always broke into the same elements in the same proportions. -
Period: to
John Newlands
He was a analitic british that prepared on 1863 a table of elements ordering them about their atomic number, he also said that every 8 elements have similar properties. -
Period: to
Max Planck
He was considered the creator of the quantum theory -
Period: to
Thompson
In 1897 thompson discovered the electron. -
Period: to
Meyer and Mendeleev
The periodic law was developed independently by Dmitri Mendeleev and Lothar Meyer in 1869. Mendeleev created the first periodic table and was shortly followed by Meyer. They both arranged the elements by their mass and proposed that certain properties periodically reoccur. Meyer formed his periodic law based on the atomic volume or molar volume, which is the atomic mass divided by the density in solid form. -
Period: to
Ernest Rutherford
Revolution in Mexico.
He discovered the proton, and he said atoms consisted largely of empty space with just a few electrons while most of the mass was concetrated in the center which he termed the nucleus. -
Period: to
Neil Bhor
The world war I started on 1914.
He stipulated that the electrons orbit the nucleus at fixed energies and distances able to jump from one level to another but not to exist in the space between. -
Period: to
Moseley
was an English physicist, whose contribution to the science of physics was the justification from physical laws of the previous empirical and chemical concept of the atomic number. This stemmed from his development of Moseley's law in X-ray spectra. -
Period: to
James chadwick
He discovered a particle in the nucleus of the atom that is called neutron -
Period: to
Heisenberg
The world war 2 began.
He showed it was imposible to determine the speed and position of the electrons as they move around the atom.