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500 BCE
Leucippus
Leucippus, a Greek philosopher, stated that matter was homogeneous, but consisted of an infinite number of small indivisible particles. -
400 BCE
Democritus
Democritus, a Greek philosopher, thought that all matter is composed of all indivisible elements. -
300 BCE
Aristotle
Aristotle believed that instead of matter being made of tiny particles (atoms), matter was fundamentally air, water, fire, and earth. He disagreed with Democritus's theory about atoms and greatly slowed down the evolution of the atomic theory, by saying that it did not exist. -
500
Alchemy
Alchemy is the art of understanding, deconstructing, and reconstructing of matter. It is composed of the four basic elements of matter--water, fire, air, and earth. Through the study of alchemy, scientists have succeeded in obtaining real world element. It also layed down the foundation of the modern Periodic Table of Elements. -
1494
George Bauer
George Bauer laid the foundations of modern chemistry; developed systematic metallurgy and medicinal application of minerals (respectively). -
Giordano Bruno
Bruno believed that god was present in every atom. -
Paracelsus
Paracelsus, a 16th-century Swiss natural philosopher, was a seminal figure in the history of chemistry, putting together in an almost impenetrable combination the Aristotelian theory of matter, chemical correspondences, mystical forms of knowledge, and chemical therapy in medicine. -
Robert Boyle
Robert Boyle attempted alchemy or turning regular metals into gold. He made gas chambers to study from. Unlike the Greek philosophers, he did physical experiments. Boyle also thought that elements are composed of 'corpuscles' of various types and sizes that are able to organize themselves into groups that represent different chemical substances. He also was able to distinguish between a mixture and a compound. -
Isaac Newton
Newton proposed a mechanical universe where small solid masses were in motion. He believed that there were little tiny pieces of mass that were 'swimming' everywhere. Newton also began to understand that atoms and particles are not stationary. -
Joseph Gay-Lussac
French chemist Joseph Louis Gay-Lussac proposed two fundamental laws of gases in the early 19th century. While one is generally attributed to a fellow countryman, the other is well known as Gay-Lussac’s law. His daring ascents in hydrogen-filled balloons were key to his investigations. -
Antoine Lavoisier
Lavoisier was known for his experimentation skills. One of his favorite experiments being turning HgO into Hg+O. He used this experiment to help himself come up with the Law of Conservation. The law states that matter cannot be made or destroyed. He also hints at the rearrangement of matter in reactions. Matter rearranged, but never disappeared. -
Amedeo Avogadro
Amedeo Avogadro is best known for his hypothesis that equal volumes of different gases contain an equal number of molecules, provided they are at the same temperature and pressure. His hypothesis was rejected by other scientists. It only gained acceptance after his death. It is now called Avogadro's law. -
Joseph Proust
Joseph Proust came up with the law of definite proportion, saying proportion by mass of the element in a given compound is always the same. -
John Dalton
Dalton did a lot of library research. He looked at almost every scientist or philosopher in history who had any conception of atoms whatsoever. After he completed his research, he compiled it into what we call Dalton's Theory. -
Jons Jakob Berzelius
Jons Jakob Berzelius compiled a table of relative atomic weights, where oxygen was set to 100, and which included all of the elements known at the time. This work provided evidence in favor of the atomic theory proposed by John Dalton: that inorganic chemical compounds are composed of atoms combined in whole number amounts. -
Henri Becquerel
Henri Becquerel was studying the fluorescent properties of uranium salts and placed a piece of the uranium salt on top of a photographic plate wrapped in black paper. He discovered, upon development, that the plate was exposed in the shape of the uranium sample Becquerel discovered radioactivity. -
J.J. Thomson
Thomson created the cathode ray, which is a tube that when a high voltage current is sent through it and the atoms hit the outside of the tube it glows. By doing so, Thomson was able to test the polarity of the atoms by placing a magnet next to the cathode ray. He found out that they were almost all negative, or beta particles. -
Ernest Rutherford
Rutherford discovered that:
An alpha particle (α=He^+2) is positive
A Beta particle (β=e-) is negative
A neutral particle (ϒ) is light He also created the gold foil experiment. By doing this experiment, he discovered that there was something in the center of the atoms, called the nucleus. This led to his nuclear model of an atom. -
Max Planck
Max Planck, a German physicist, is best known as the originator of the quantum theory of energy for which he was awarded the Nobel Prize in 1918. His work contributed significantly to the understanding of atomic and subatomic processes. -
Niels Bohr
Bohr studied the structure of an atom and suggested that electrons didn't spiral into the nucleus, but orbit in different levels. This allowed for the creation of the Bohr model, or the quantum model. The more energy an atom gives off, the closer it is to the nucleus, the more it absorbs, the farther away. It was almost error less when he won the Nobel Prize for it, however over time, other chemists slightly changed it. -
Robert Millikan
Robert Andrews Millikan was an American experimental physicist honored with the Nobel Prize for Physics in 1923 for the measurement of the elementary electronic charge and for his work on the photoelectric effect. His oil drop experiment helped to quantify the charge of an electron, which contributed greatly to our understanding of the structure of the atom and atomic theory. -
Louis de Broglie
Louis de Broglie was an eminent French physicist. He gained worldwide acclaim for his groundbreaking work on quantum theory. In his 1924 thesis, he discovered the wave nature of electrons and suggested that all matter have wave properties. -
Werner Heisenberg
Heisenberg is best known for his uncertainty principle and theory of quantum mechanics, which he published at the age of twenty-three in 1925. He was awarded the Nobel Prize for Physics in 1932 for his subsequent research and application of this principle. -
Erwin Schrodinger
In 1926 Erwin Schrödinger, an Austrian physicist, took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom. -
Arthur Compton
Compton is best known for demonstrating the "Compton effect," which occurs when high energy photons (such as X-rays) collide with a target, and transfer part of that energy to a single electron -- supporting Einstein's particle theory of light. Compton shared the 1927 Nobel Prize in Physics for this discovery. -
James Chadwick
Chadwick discovered neutrons, which allowed for the fission of uranium and the creation of bombs. -
Murray Gell-Mann
Murray Gell-Mann. Murray Gell-Mann is an American physicist who is credited with the introduction of the concept of quarks. He won the 1969 Nobel Prize for physics for his groundbreaking work on the description and classification of subatomic particles. -
Carlo Rubbia
Carlo Rubbia shared with Simon van der Meer the Nobel Prize for Physics for the discovery of the massive, short-lived subatomic W particle and Z particle. These particles are the carriers of the so-called weak force involved in the radioactive decay of atomic nuclei. Their existence strongly confirms the validity of the electroweak theory, proposed in the 1970s, that the weak force and electromagnetism are different manifestations of a single basic kind of physical interaction. -
Peter Higgs
Peter Higgs is a British physicist who was awarded the 2013 Nobel Prize for Physics for proposing the existence of the Higgs boson, a subatomic particle that is the carrier particle of a field that endows all elementary particles with mass through its interactions with them. He shared the prize with Belgian physicist François Englert.
