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465 BCE
*Democritus - Greece
In Democritus' atomic theory, he theorized that everything is made of tinier parts of itself. This theory originally came from his mentor, Leucippus. They thought that when you cut something in half enough, eventually you'd get smaller versions of that item. For example, cheese is made of tiny, bouncy, cheeses. -
340 BCE
Aristotle - Greece
Aristotle thought that matter was made of only five elements; air, earth, water, fire and Aether, which was a substance he believed was made if stars. Matter could be a combination of those five elements or one of the five themselves. This contribution was a pain to scientific progress and delayed the completion of the Atomic theory. -
776
Abu Musa Jabir ibn Hayyan - Iran
In 776, Abu Musa Jabir ibn Hayyan started to gain an interest in alchemy. His important contribution to science is the Jabirian Corpus, which is a type of arithmology that was to determine the quantity of the four natures. He also made many lab equipment we still use today. He made an alembic for distillation and discovered acids of different types. -
1250
Albertus Magnus - Germany
Albertus Magnus was a German priest that discovered arsenic and isolated it. It was the first ever element to be isolated and he also made himself famous for having a philosophers stone. This stone was told to have been able to transform into any element you'd want. Obviously it wasn't real but he made people believe it was. -
Robert Boyle - Republic of Ireland
Robert Boyle contributed by creating Boyle's Law, which states that when the volume of a gas decreases, the pressure increases. Knowing that the conclusion of his experiments could only be explained if gasses were made of tiny particles. He also introduced bases in acids, the idea of an element, and chemical tests. -
Henry Cavendish - United Kingdom
Henry Cavendish was a chemist that was the first to figure out the composition of water, that it was made with hydrogen and oxygen. He also created a way in order to have hard water and soft water. Other than that, he also studied fermentation. -
Antoine Lavoisier - France
Antoine Lavoisier is famously known for coming up with the Law of Conservation of Mass. This law states that matter is neither created nor destroyed during a chemical reaction or physical transformation. In this law, the product of the reaction equates to the sum of the reactants. He also gave names to multiple substances including oxygen. -
*John Dalton - United Kingdom / Dalton's theory was the first, experimented and tested, theory on the atom
In Dalton's atomic theory, atoms make up all matter, all atoms are identical when the same element, compounds are made of atoms, and that a chemical reaction rearranges the atoms. To figure this out Dalton experimented with gasses and based his theory on the law of conservation of mass and law of constant composition. He also measured the world's first atomic weight, studied gases and discovered the Law of multiple proportions; compounds are formed from a combination of two or more elements. -
Amedeo Avogadro - Italy
Amedeo Avogrado was an Italian scientist that is famously known for creating Avogrado's Law, which states that all gases at equal volume and equal temperature and pressure contain an equal number of molecules. -
Dmitri Mendeleev - Russia
Dmitri Mendeleev was a chemist that organized the elements depending on their atomic mass and physical or chemical characteristics. He made it so that the atomic mass was in rows and the properties were in columns. This is now known as the periodic table and because of this, Mendeleev discovered three new elements at this time because of this. -
Marie/Pierre Curie - Poland
Marie and Pierre Curie are wife and husband that studied radiation together. They won a Nobel Prize for discovering that radioactivity occurs in the atom itself and isn't about the arrangement of the atom. They even found two new elements named radium and polonium together. Unfortunately, Pierre died before both could accept another Nobel Prize, but this time for chemistry. Only Marie got a Nobel Prize for the newly found elements. -
*J.J. Thomson - United Kingdom / J.J. Thomson developed the plum pudding model for the atom
J.J. Thomson discovered electrons, negative charged particles, in an atom.He also discovered that atoms contain a positively charged nucleus. He also noticed that the nucleus was surrounded by a positive charge to cancel out the negative particles. To discover the electrons, he used cathode rays, which have a negative charge. He also studied neon rays. -
William Ramsay - United Kingdom
William Ramsay was a chemist that discovered many noble gases in his time. He discovered argon, helium, neon, krypton, and xenon. He even proved that radon was a part of the noble gasses. He also figured out that helium is always produced by radioactive decay in the element radium. -
*Ernest Rutherford - New Zealand / Ernest Rutherford was a chemist that worked on the gold foil experiment which lead him to the creation of the nuclear model
In the gold foil experiment, Rutherford noticed that when he shot alpha particles through a very thing piece of gold foil, some of them went through but some of them bounced back. He concluded, from this experiment, that there is a positive charge on the nucleus and that the atom is mostly made of empty space. Other than his atomic theory, Rutherford also discovered alpha and beta rays, discovered the law of radioactive decay, and recognized alpha particles as helium nuclei. -
*Niels Bohr - Denmark / Neils Bohr was the man that developed the planetary model for the atom.
Rutherford's model didn't describe how the electrons stayed with the nucleus. Rutherford's model was also unstable. So, Neils Bohr modified it by claiming that electrons orbit around the nucleus, like in the solar system. He also claimed that the atom has shells and in the first shell, closest to the nucleus, there's only two electrons. The second has eight and the third has eighteen. He applied his atomic theory to the periodic table too. He also contributed to the making of quantum mechanics. -
Werner Heisenberg - German
Werner Heisenberg worked on the model of the atom. He found it limiting to only described the physical properties of the atom, so he thought of looking at it in a mathematical way. This was called matrix mechanics. He also came up with the theory of wave mechanics in the age of 23! Which is resulted him to receiving a Nobel Prize. -
*Erwin Schrodinger - Australia / Erwin Schrodinger was the physicist who discovered the quantum model. The problem with Bohr's planetary model was that it couldn't explain heavier atoms.
So Schrodinger started to work on a mathematical way of finding an electron. This model estimated where an electron might be, but doesn't say exactly where. To envision what this looks like, it's a cloud surrounding the nucleus and the cloud gets thicker the more electrons there is in that area. He also explained the movement of an electron as a wave, which is the same with Heisenberg but he visualized it other than only using math, which is what Heisenberg did. -
Louis de Broglie - France
Louis de Brogile is a french scientist that discovered the theory of wave particle duality. This states light and matter have characteristics of waves. He won a Nobel Prize for that discovery. -
James Chadwick - United Kingdom
James Chadwick was the one who discovered the existence of neutrons in the middle of atoms. Neutrons don't have a positive nor negative charge. They also have the atomic weight as a proton. -
Irène Joliot-Curie - Italy
Irène Joliot-Curie continued the legacy of her parents by studying radioactivity. Then, along with her husband, they found that you could make radioactive elements from stable elements. They turned aluminum into something radioactive which lead them to win a Nobel Prize in chemistry. -
Rosalind Franklin - United Kingdom
Rosalind Franklin was the chemist that took the picture of the DNA. The picture was known as Photograph 51 and showed a wet form of the DNA. This picture was shown to Watson and Crick, who was working on the DNA model, without Franklin's knowledge. Watson and Crick later got a Nobel Prize without crediting Franklin's work... -
Lise Meitner - Austria
Lise Meitner discovered nuclear fission. This is the process of splitting a nucleus in order to get smaller fragments. She was also the first woman to ever be a physics professor in Germany obviously before the Nazis took over. Her along with her partner, Hahn, also discovered nine new elements. Hahn didn't mention Meitner's contribution to nuclear fission and Hahn got a Nobel Prize. It is only later that Meitner's work was credited and now she the 109 element named after her. -
Linus Pauling - USA
Linus Pauling was an American chemist who won two Nobel Prize by himself. One of which was his contribution to chemistry as he studied how chemical bonds worked and what would happen when they're applied to the elucidation of the structure of complex substances.
