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400 BCE
Democritus
Democritus used reasoning instead of science when he came up with his theory. He based his work off of the philosophers Leucippus and Anaxagoras. Democritus was the first person to suggest that materials were made up of smaller things. He called these things 'atomos'. He theorized that every material had its own 'type' of atomos and that no matter how small you cut something up, it would always have the same properties. He said that matter cannot be created nor destroyed. -
300 BCE
Aristotle
He believed you could understand and figure out things by simply thinking about them. He also believed that everything was a combination of the four elements: earth, fire, water, air. His theory was that a mass of incomprehensible size was everywhere; he called this 'hyle'. There was no separate 'particles' for each material, it was all one. -
1494
George Bauer
presented the first scientific classification of minerals (based on their physical properties) and described many new minerals, their occurrence and mutual relationships. -
Robert Boyle
Boyle mainly studied gases. He discussed the possibility of atoms existing. He attempted alchemy or turning regular metals into gold. He made gas chambers to study from. Unlike the greek philosophers, he was doing physical experiments. He proposed 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. -
Antoine Lavoisier
Lavoisier was known for his experimentation skills. One of his favorite experiments being turing 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. -
Amadeo Avogadro
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 Gay-Lussac
French chemist and physicist who pioneered investigations into the behaviour of gases, established new techniques for analysis, and made notable advances in applied chemistry. -
Joseph Proust
Proust stated the Law of Definite Proportions. The law states that the ratio of elements in a compound is always the same/constant. He also hinted at the 'lego'ness of matter; he believed that matter could be put together in certain patterns to make bigger, different, unique matter -
John Dalton
After he completed his research, he compiled it into what we call Dalton's Theory. His theory contained 5 parts:
-matter is composed of extremely small particles called atoms
-atoms are indivisible and indestructible
-atoms of a given element are identical in size, mass, and chemical
properties
-atoms of specific elements are different than those of other
elements
-in a chemical reaction, atoms separate, combine and/or rearrange -
Henri Becquerel
French physicist who discovered radioactivity through his investigations of uranium and other substances. In 1903 he shared the Nobel Prize for Physics with Pierre and Marie Curie. -
Max Planck
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. -
Robert Millikan
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. -
Erwin Schrodinger
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. -
Louis de Broglie
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. -
J.J. Thomson
Thomson created the cathode ray. The cathode ray is a tube that when a high voltage current is sent through it and the atoms hit the outside of the tube it glows. In this way, Thomson was able to test the polarity of the atoms by placing a magnet next to eh cathode ray. He found out that they were almost all negative, or beta particles. -
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. -
Ernest Rutherford
Rutherford's most famous experiment is the gold foil experiment. It consisted of shooting Alpha atoms into extremely thin gold foil and seeing where on the surrounding circular wall it hit. He believed they would all just go straight through. However, a very small amount went either off to the sides or back towards the Alpha atom stream. This he found meant that there was something in the center of the atoms, called the nucleus. This led to his nuclear model of an atom. -
Niels Bohr
Bohr studied the structure of an atom. He suggested that electrons didn't spiral into the nucleus, but orbit in different levels. This is called 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 errorless when he won the Nobel Prize for it, however over the years other chemists have tweaked it a bit.
