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500 BCE
The alchemists
They broke down the four basic elements and figured out their chemical composition. This helped begin the periodic table. -
427 BCE
Plato
He introduced the atomic theory. The atomic theory had ideal geometrical forms serve as atoms, then they broke down into triangles which is why the four basic elements all have their own shape. -
400 BCE
democritus
Democritus's theory explains that everything is composed of atoms, which are indivisible physically. In between atoms lies open and empty space. Atoms cannot be destroyed and there is an infinite amount of atoms. -
384 BCE
Aristotle
He did not believe in the atomic theory. In his mind, All the materials on earth weren't made of atoms, instead they were made of the four elements. -
330 BCE
Solar sytem model
It was a model that placed all planets in order. Heraclides developed this model. -
Robert Boyle
He helped develop and figure out the definition of the element. He also helped out with "the death" of the four elements and with the way people think about science. -
Lavoisier
he decomposed red calx into oxygen and mercury. He also found no way to break oxygen levels down into two or more new substances. -
solid sphere of billiard ball model
It was the first atomic model. John Dalton developed this model. He though that an atom was a solid sphere that was not able to be divided into smaller particles. -
John Dalton
His atomic theory proposed that every bit of matter was composed of atoms. They are indestructible and indivisible building blocks. -
Dmitri mendeleev
He discovered that when all known chemical elements are arranged in order by its increasing weight, the results displayed a pattern. -
J.J thomson
His experiments showed that all atoms contain small negatively charged particles that are subatomic. Thomson also proposed the plum pudding model of the atom. -
The curies
Pierre and Marie curie discovered some radioactive elements called polonium and radium, They both occur naturally in uranium minerals, -
"plum pudding" model
It shows the atom and a picture of plum pudding. It depicts the electrons as negative particles that are in a group of positive charged electrons. -
albert einstein
He mathematically proved the existence of atoms. He helped revolutionize all of science through the use of probability and statistics. -
Robert Millikan
A theory that electricity was conveyed from a minuscule unit, acceptance of the electron was gained. Millikan did great in precisely figuring out the magnitude of the electrons charge. -
Ernest Rutherford
the gold foil experiment showed what the atom consists of. It is made up of a massive, small, and positively charged nucleus with negatively charged electrons being at a large distance from the the center. -
Neils bohr
He proposed a theory for the hydrogen atom. It was based on the quantum theory that energy is only transferred in specific well defined quantities. Electrons should be moving around the nucleus while its only in a prescribed orbit. -
Henry G.J. Mosely
He measured and observed the xray spectra that contained various chemical elements using the diffraction in crystals. He discovered a systematic relation that was between atomic number and wave length. -
Werner heisenberg
He formulated quantum mechanics in the terms of matrices and by discovering the uncertainty principle. It states that a particles position and momentum cant be exactly be known. -
Electron Cloud model
Developed by Erwin Schrodinger and Werner heisenberg. This model visualtizes the most probable location of electrons in an atom.
