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100
500th BCE, Democritus
Democritus hypothesized that all matter is composed with tiny indestructible units, called atoms in 5th century BCE. Democritus performed no experiments and had only little evidence, his theory was kept alive. The atomic theory stated that the characteristics of an object are varies by the shape of its atoms. Therefore, they thought that sweet things are made out of smooth atoms, bitter things are made of sharp atoms. He hypothesized that atoms are indivisible. -
100
5th Century BCE, Democritus Atom Model
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Antoine Lavoisier
Antoine Lavoisier discovered in 1803 that there was no change in mass upon formation or decomposition of the atom. He hypothesized that this should be true of all chemical changes and further experiments proved that he was right. This principle is now called the law of conservation of mass. -
John Dalton
John Dalton did not quite “invent” anything but he proved the atomic theory. The atomic theory is that all matter is made of atoms. He thought though that the atom is the smallest piece and cannot be broken down into smaller pieces. J.J Thomson proved him wrong. -
J.J. Thomson
In 1897 the British physicist Joseph John (J. J.) Thomson (1856–1940) discovered the electron in a series of experiments designed to study the nature of electric discharge. JJ. Thomson discovered that atoms can be cut. He found this out while studying rays traveling between charged metal plates in a vacuum tube. He discovered that the rays were consisted of negatively charged particles. He had just discovered electrons. He discovered all of this on a trip from America. Since electrons are so sma -
Marie & Pierre Curie (1898)
Marie and Pierre Curie discover the elements radium and in 1898. Also, she hypothesized that the radiation was not the outcome of some interaction of molecules but must come from the atom itself. The hypothesis was an important step in disproving the ancient theory from 5th century that atoms are not divisible. -
Max Planck
Max Planck discovered that energy was made of individual units, or quanta in 1900. He is the originator of the quantum theory. This theory revolutionized the understanding of atomic and subatomic processes. Max Planck and Albert Einstein constituted the basic theories of 20th century physics. Both led to industrial and military applications that affect everything in modern life. -
Thomson's Plum Model
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Albert Einstien
Albert Einstein invented many theories of science in his life that would later be used for different things like the atomic bomb. Some of them were the particle theory, Einstein field equations and the Photoelectric effect. Albert Einstein invent the famous equation (E=Mc2). He also invented more real life things life a refrigerator and a self adjusting camera. He also invented a new method of counting and determining the size of the atoms or molecules in a given space and in the other he explai -
Rutherford Model
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Bohr Model
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Neils Bohr
Neils Bohr made that the theory that electrons circle around the nucleus in the middle of the atom. Also he invented that there are different energy levels around the nucleus and that how more far you go from the nucleus the bigger the electric charge gets. Also he was one of the scientists who in World War 2 invented the atomic bomb that was later dropped on Japan. -
Ernest Rutherford
Ernest Rutherford proved that inside an atom there is a nucleus, which was thought before to be just empty space. Ernest Rutherford also proved that there was positive charge in the middle atom by doing the gold foil experiment which was shooting a particle through a sheet of gold and when he did that the particle bounced of and so it proved that there was something of positive charge in the atom. -
Modern Electron Cloud
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James Chadwick
In 1932, James Chadwick conducted a experiments that proves the existence of Neutrons. Although they knew that it existed, at that time, it was still being experimented. He was able to determine that the neutron did exist and that its mass was about 0.1 percent more than the proton's. He published his findings with characteristic modesty in a first paper entitled "Possible Existence of Neutron." -
