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500 BCE
The Alchemists
Believed there were four elements: earth, wind, water, and fire. This was the beginning of scientific thinking regarding atomic theory -
450 BCE
Democritus
Democritus proposed that all matter up of tiny particles called átomos. This was the first theory relating to the atom and got people thinking about what matter was really made up of. -
427 BCE
Plato
Plato proposed that there were 4 elements: earth, wind, water, and fire, he also thought that all atoms were geometric in shape. This was one of the earliest examples of thinking about the atom and its makeup. -
Robert Boyle
Boyle proposed that elements cannot be broken down further and still retain the properties of that material. Boyle’s studies ushered in a new age of scientific study regarding the atom and did away with alchemy. -
Antone Lavoisier
Lavoisier created the Law of Conservation of Matter which proposed that all matter could neither by created nor destroyed and set a basis for further scientific study of the atom. -
John Dalton
Proposed that elements are made of tiny particles called atoms and different elements atoms have different weights and properties. Dalton was the first person to propose the idea of the atom and his theory is still the basis of atomic theory to this day. -
Billiard Ball Model
The Billiard Ball Model was created by John Dalton in 1803 -
Amadeo Avagadro
Avagadro created Amadeo’s Law which stated that elements have the ability to exist in the form of molecules. This proposed that elements were the building blocks of larger materials. -
Dimitri Mendeleev
Mendeleev created the periodic table and is considered the father of the atom. Mendeleev’s discovery created a way for future scientists to organize atoms. -
JJ Thompson
Thompson discovered the electron in 1897. This brought about the idea that atoms could be made of smaller particles. -
Pierre & Marie Curie
Pierre & Marie Curie discovered Radium and Polonium. They also proved that atoms could be broken down using radiation. -
Plum Pudding Model
The Plum Pudding Model was created by J.J. Thompson in 1904 -
Albert Einstein
Albert Einstein with the help of a botanist proved the existence of the atom using a microscope, water, and a grain of pollen. This meant the atom was no longer theoretical and scientists now had a base for further studies of the atom. -
Robert Millikan
In 1910 Millikan accurately measured an electrons charge. -
Ernest Rutherford
Proposed that all atoms had a “core” or a nucleus. This expanded on earlier knowledge of the atom and its makeup and is still used today when discussing the atom. -
Henry G.J. Moseley
Mendeleev was the father of the periodic table. However, Moseley reorganized Mendeleev’s periodic table and is considered the modern father of the atom -
Solar System Model
The Solar System Model was invented by Neil Bohr -
Neils Bohr
Bohr proposed that electrons travel in orbits around the nucleus and the number of electrons determines the elements properties. This discovery furthered scientific knowledge because this built on the already prominent idea of atom. -
Electron Cloud Model
The Electron Cloud Model was created by Erwin Schrodinger in 1926 -
Erwin Schrodinger
Schrodinger proposed the electron cloud model and also formed an equation to calculate an electrons energy levels -
Werner Heisenberg
In early 1927, Heisenberg proposed the uncertainty principle which states that there is a limit to what we can know about a particle. for example, you can know an objects precise position, but less about its momentum. -
James Chadwick
James Chadwich discovered the neutron in 1932. Which led to further understanding of the makeup and roles of atoms and the particles that make them up.