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400 BCE
Democritus
Democritus developed the idea of atoms around 400 BCE Greece. He knew that substances were not able to split in half anymore. He called those particles atoms. If Democritus never came up with the idea of atoms, no discovery of elements or atoms could have been made without this information to build from. -
350 BCE
Aristotle
Aristotle was a philosopher and scientist who lived in classical Greece from 384-322 BCE. He studied how substances interacted with other substances and the environment, as well as forms of matter. His main contribution to chemistry was his theory that there were 4 main elements that were the building blocks for all substances. Though his ideas of only 4 main elements aren't accurate today, his idea of elements being the base of all matter is still widely accepted and taught in chemistry. -
700
Abu Musa Jabir ibn Hayyan
Abu Musa Jabir Ibn Hayyan-Persia He created the idea of chemical bonds linking elements together. He also created the Alembic which is a simple way to distill liquids by connecting two bottles with a tube and using heat. Altogether, Jabir developed many ways of how to experiment in chemistry. -
1245
Albertus Magnus
Saint Albertus Magnus was a German philosopher who studied all kinds of topics ranging from natural sciences to economics. He didn't exactly have any important discoveries but he did expand upon Aristotle's work which led to a better understanding of the natural sciences by the population. Without the teachings and experimentation of Albertus Magnus the works of Aristotle may not have been as crucial to the history of matter and the study of science may have been neglected. -
1440
Printing Press
The printing press was invented in Holy Roman Empire by the German Johannes Gutenberg, based on existing screw presses. The press made it possible for knowledge to be spread widely and read by anyone taught that skill. Gutenberg adapted existing technologies to printing purposes, as well as making inventions of his own. The printing press changed the world because it profoundly impacted the transmission of knowledge. -
Vacuum Pump
The vacuum pump was invented by the German Otto von Guericke in 1650 to study a vacuum and what role air played in combustion and respiration. This invention is significant to chemistry because it led to research about the properties of a vacuum and later resulted in the development of the vacuum tube. -
Robert Boyle
Known to be one of the founders of modern chemistry, Robert Boyle was a famous figure born out of Ireland. His most important work relating to chemistry is Boyle's Law written in 1662 which states that if the volume of a gas is decreased, the pressure increases at a proportional rate. His works are still relevant to chemistry today as he defined the modern idea of an element and also created the litmus test for acids and bases. -
Electric Generator
Several years after creating the first vacuum pump Otto von Guericke invented the first electric generator in 1663. The device generated static electricity through friction against a revolving sphere of sulfur. The invention was important to chemistry because it was the beginning of a new branch of study known as electrochemistry. Von Guericke also used his invention to demonstrate how like charges repelled each other, which would become important later for atomic theory. -
Analytical Balance
The first balance capable of measuring to the nearest 0.0005g was the analytical balance. This type of balance was developed around 1750 by Joseph Black, a Scottish chemist and physician. The balance was the most precise of its time and as time went by it was improved upon, becoming important in demanding chemistry laboratories. -
Henry Cavendish
Canvendish-England created an investigation of the composition of hydrogen or what he called ¨atmospheric air.¨ He described the composition of water and made the first accurate measurement of the density of the earth. -
Antoine Lavoisier
Lavoisier-France indicates that mass is neither created nor destroyed in any ordinary chemical reaction. This was a large influence on both the history of chemistry and the history of biology. He proved that the mass of the products in a chemical reaction is equal to the mass of the reactants. Lavoisier helped construct the metric system and wrote the first extensive list of elements. -
John Dalton
Dalton-England created the ¨modern atomic theory¨ which proposed that all matter was composed of atoms. While all atoms of an element were identical, different elements had atoms of varying size and mass. Dalton was the first scientist to explain the behavior of atoms by their measurement and weight. He stated that atoms cannot be created or destroyed based on the Law of the Conservation of Mass. Dalton also researched color blindness, sometimes referred to ¨Daltonism¨ in his honor. -
Amedeo Avogadro
Amedeo Avogadro was a scientist from Italy who hypothesized that equal volumes of different gasses contain an equal number of molecules if they are the same in temperature and pressure. This hypothesis later became known as Avogadro's Law which wasn't accepted until after his death. -
Dmitri Mendeleev
Mendeleev was a Russian chemist who devised the periodic table of elements. He discovered that the properties of elements were functions of their atomic weights which became known as the Periodic Law. His periodic table of elements had 7 periods which each contained elements whose properties were similar. This discovery had a great influence on atomic theory because it helped scientists categorize elements based on their molecular properties. -
William Ramsay
Ramsey-England used methods to remove all known gases from the air. He discovered argon, neon, xenon, and krypton. According to where the elements were located in the periodic table, Ramsey indicated that at least 3 more noble gases may exist. He revealed that helium is endlessly produced during the radioactive decay of radium. This was key for the understanding of nuclear reactions. -
J.J Thomson
Thomson-England constructed experiments to try and find a conclusive answer about cathode rays. He founded that cathode rays were made up of an unknown negatively charged particle. Thomson also made the discovery and identification of the electron. -
Marie and Pierre Curie
Marie and Pierre Curie-France worked on the study of radioactivity. They discovered the elements polonium and radium. The work of Marie and Pierre Curie, which by its nature dealt with changes in the atomic nucleus, led the way towards the modern understanding of the atom as an existence that can be split to release enormous energy. -
Ernest Rutherford
Rutherford-England made up the Rutherford model, declaring that a very small positively charged nucleus was orbited by electrons. He set up an experiment to use the alpha particles which were emitted by a radioactive element as probes to the unseen world of atomic structure. -
Niels Bohr
Bohr-Denmark The electrons in the Rutherford model were unstable because electrons would lose energy and spiral into the nucleus. Bohr changed the Rutherford model by having the electrons move in orbits of fixed size and energy. This advanced model is called the Bohr atomic model. -
Louis de Broglie
Brogile-France His ideas were the basis for developing the general theory of wave mechanics. This theory transformed the knowledge of physical phenomena on the atomic scale. Broglie gained worldwide acclaim for his groundbreaking work on quantum theory. -
Erwin Schrödinger
Erwin Schrödinger was an Austrian physicist who, in 1926, proposed of a quantum mechanical atomic model which was roughly based on, but somewhat unlike Bohr's model from 1913. The quantum mechanical model predicts the odds of the location of an electron rather than defining its path. This discovery directly related to the advancement in atomic theory and without this model the idea of sub-energy levels and the wave equation might not exist. -
Werner Heisenberg
Heisenberg-Germany He discovered the uncertainty principle, which states that it is impossible to know simultaneously the exact momentum and position of a particle. He developed the theory of quantum mechanics which he published in 1925 at age twenty-three. -
James Chadwick
Chadwick-England He discovered the neutron, the information that led him to this discovery was his proof that it had consisted of a neutral particle with about the same mass as a proton. Chadwick proved that radiation causing the ejected particles in Irene Joliot-Curie's experiments was more lively then it could be accounted for by photons. This improved the knowledge on the structure of atoms. -
James Chadwick
James Chadwick was a scientist from England who made the discovery of the neutron in 1932 after the proton had been discovered in 1919. Chadwick was able to determine the existence of the neutron using methods from Federic and Irene Juliot-Curie. This discovery assisted in advancing the knowledge of the atom and the current understanding of the atom could possibly be nowhere near where it is without this discovery. -
Irene Joliot-Curie
Irene Joliot-Curie was a French scientist who was largely influenced by her parents Marie and Pierre Curie. Her most important contribution to chemistry was the discovery that radioactive elements could be produced artificially from stable elements. She was awarded the Nobel Prize in Chemistry in 1935 and her findings sparked further research into radioisotopes. Her works impacted the world of medicine and helped other researchers discover new ways to treat diseases with radioactive isotopes. -
Lise Meitner
Lise Meitner was an Austrio-Hungarian physicist who discovered nuclear fission in 1938. This discovery was huge for the world of chemistry because it explained the chemical reaction that an atom goes through when it is split and how large amounts of energy are released in the reaction. It also resulted in an interest of harvesting the energy released for use, but was only utilized widely for the development of atomic bombs like in the Manhattan Project. -
Linus Pauling
Linus Pauling was an American who recieved 2 Nobel Prizes and is widely known as a founder of quantum chemistry and molecular biology. His most important works relating to chemistry were his publishings which explained the valence bond theory, electronegativity, orbital hybridization, and resonance. These ideas proposed by Pauling futher supported atomic theory by adding an explanation for how substances interacted with each other through bonds. -
Rosalind Franklin
Rosalind Franklin was a British scientist who studied the structure of DNA. She worked with a colleague to acquire x-ray photographs of DNA and was able to produce an extremely vivid x-ray called Photo 51. This photograph is what led Watson and Crick to their famous model of DNA published in 1953. This discovery is relevant to atomic theory because it deals with the molecular structure of natural substances just like previous models, only this discovery is more biological that chemical.
