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3000 BCE
Precision Balance
Country of Origin: Egypt and Ancient Rome
Contribution: At the time it was used to establish the cost of goods and is currently used to make accurate measurements of the mass of an object. -
721 BCE
Abu Musa Jabir ibn Hayyan
Country: Iran
Contribution: He emphasized the importance of experimenting in chemistry. He began his experimentation with matter and then started experimenting with matter that he could mix together, which led him to identifying new substances. -
460 BCE
Democritus
Date: Lived 460-370 BCE
Contribution: He hypothesized that the physical world was made up of an infinite amount of moving atoms and claimed that atoms are all the same except for in shape, arrangement, position, and magnitude.
Observations: He broke sea shells in half continuously until he ended up with powder. He also adopted the theory from his teacher Leucippus.
Discovery: Everything is made up of atoms, they are indestructible, they are always moving, and between atoms is just empty space. -
355 BCE
Aristotle
Date: 355 and 323 BCE
Country: Ancient Greece
Contribution: Aristotle believed that all things on Earth were composed of a combination of the four elements, water, earth, fire, or air (plot twist Aristotle was the first avatar) -
1250
Albertus Magnus
Country: Germany
Contribution: He was the first to present natural science as legitimate in the Christian world; he promoted Aristotelianism. He also isolate arsenic, which was the first element isolated since antiquity. -
1440
Printing Press
Country of Origin: Germany
Contribution: The purpose was to mass produce works and literature. The printing press allowed for mass production of scientific works and allowed for these works to spread globally at a faster rate. -
Robert Boyle
Country: United Kingdom
Contribution: He created Boyle's Law, which states that the volume of a given amount of gas held at a constant temperature varies inversely with the pressure, by conducting experiments where he created a vacuum using an air pump. -
Vacuum Tube and Electric Generator
Country of Origin: Germany, created by Otto von Guericke
Contribution: The electric generator provides static electricity by creating friction on a revolving ball of sulfur. Guericke created the air pump which he used to create the vacuum tube. His studies showed that light travels through a vacuum and sound does not. -
Henry Cavendish
Date: 1766 and 1797
Country: United Kingdom
Contribution: (1766) He published a work on chemistry stating that he created Hydrogen (as he called it "inflammable air"). In the 1780's he developed a general theory of heat and it contained the principle of conservation of heat. In 1797, he was the first to measure Earth's density using Isaac Newton's theories. He also found the composition of water. He also started a gas theory. -
Antoine Lavoisier
Date: 1770's
Country: France
Contribution: Lavoisier was a co-author of the modern system of naming chemical substances. He also developed the Law on Conservation of Mass, which states that mass is neither created or destroyed during a chemical reaction, it is instead conserved. -
John Dalton
Country: England
Observations: He based his theory of partial pressures on the idea that only like atoms in a mixture of gases repel one another, whereas unlike atoms appear to react indifferently toward each other. This was later found to be incorrect, but it did help him abolish the theory (used for centuries by other philosophers) that all atoms are the same. He focused on finding the relative mass of each atom, although he never performed research in the field of Chemistry. -
John Dalton
Observations: For formulating the Law of Multiple Proportions, Dalton measured the mass of various elements according to the way they combined with fixed masses of each other, meaning that these elements combined into fixed proportions.
Discoveries: Dalton created the Atomic Theory (1808) as well as the Law of Multiple Proportions and the Law or Partial Pressures. Also created the first chart of atomic weights.
Contribution: Hypothesized that all atoms of elements have a different size and mass. -
Avagodro
Country: Italy
Contribution: He created Avogadro's Principle, which states that equal volumes of gases at the same temperature and pressure contain equal numbers of particles. -
Dmitri Mendeleev
Date: 1868-1870
Country: Russia
Contribution: Mendeleev created the first and earliest version of the periodic table in 1869. In 1868, he found that atomic mass could be put in an order to arrange the elements and put them into groups, thus discovering the periodic law. -
William Ramsey
Country: Scotland
Contribution: Ramsey discovered a number of elements such as Argon, Neon, Helium, Krypton, and Xenon while trying to understand the composition of the atmosphere. -
JJ Thomson
Country: England
Contribution: He discovered the electron and in 1906 he received the Nobel Prize for Physics.
Observations: His discovery was a result of trying to solve the controversy regarding the nature of cathode rays. He used a vacuum technique by studying electric discharge of the cathode ray tubes that proved that these rays were made or particles.
Discoveries: He found that electrons were found in all kinds of matter. He also created the plum pudding structure. -
Marie and Pierre Curie
Country: France and Poland
Contribution: They had studied radioactivity, which ultimately led to the discovery of radium and polonium. -
Niels Bohr
Country: Denmark
Contribution: He brought insights to the quantum theory as well as electrons and their movement.
Observations: He combined Rutherford's description of the nucleus and Planck's theory about quanta to create a model of an atom.
Discoveries: He created the Bohr model of an atom and discovered that electrons can move in an orbit around the nucleus of atom and that they can jump energy levels. -
Ernest Rutherford
Country: England
Observations: While at Cambridge (1896) he studied ultraviolet radiation and then radiation emitted by uranium. At McGill University, he and a colleague found that thorium emitted a gaseous radioactive product called emanation. 1902-03 he and Frederick Soddy of McGill University discovered the transformation (disintegration) theory to explain radioactivity. -
Ernest Rutherford
Observations: While at the University of Manchester, Rutherford and his student Thomas Royds were able to isolate some alpha particles and perform a spectrochemical analysis, which proved that particles were helium ions. He and Bertram Borden Boltwood redetermined the rate of production of helium by radium. -
Ernest Rutherford
Country: England
Contribution: He won the Nobel Prize for Chemistry. He developed an electrical counter for ionized particles (was perfected by Hans Geiger and named the Geiger Counter). Created the atomic model which was later elaborated by Bohr (Bohr atomic model).
Discoveries: He created the alpha and beta radiations. Transformation theory claimed that radioactivity came from within an atom and an emission of alpha or beta particles signified a chemical change from one element to another. -
Lise Mietner
Country: Austria and Germany
Contribution: With the help of Otto Hahn, they discovered protactinium. In 1923, she also discovered the Auger Effect, which is a radiation-less transition. The Auger Effect was named after a French scientist who discovered it 2 years after Mietner made the discovery -
Werner Heisenberg
Country: Germany
Contribution: He created the Heisenberg Uncertainty Principle, which states that it is not possible to know precisely both the velocity and the position of a particle at the same time. He also created the theory of quantum mechanics. -
Erwin Schrodinger
Country: Austria
Contribution: Added to the wave of theory of matter and the quantum mechanical model of the atom.
Observations: Using math equations, he made advances in quantum mechanics
Discoveries: The quantum mechanics model introduced the concept of sub-energy levels. He created the Schrodinger equation, which is the basic equation for quantum mechanics and has direct relation to the mechanics of an atom. -
Louise de Broglie
Country: France
Contribution: He created the de Broglie equation that predicted that all moving particles have wave characteristics and relates each particle’s wave length to its frequency, mass, and Planck's constant. -
Linus Pauling
Country: United States
Contribution: Pauling learned about electron diffraction, and used this technique of scattering electrons from the nuclei of molecules to determine the structures of important substances, leading to developing an electro-negativity scale where he assigned a number representing a particular atom’s power of attracting electrons in a covalent bond. He created a valence theory, which stated that a molecule could be described by an medial structure that was a hybrid of others. -
James Chadwick
Country: United Kingdom
Contribution: He was studying beryllium, when exposed to bombardment by alpha particles, exposed an unknown radiation that released protons from the nuclei of various substances. This unknown substance was equal in mass to a proton but did not have an electric change, these are called neutrons. -
Irene Joliot-Curie
Country: France
Contribution: She conducted research on the actions of neurons on heavy metals. This research led to the discovery of uranium fission. -
Rosalind Franklin
Date: 1951-1953
Country: England
Contribution: Franklin and her lab partner Maurice Wilkins worked on a DNA lab project and came very close to solving the DNA structure; is credited for being to first to use the double helix model for DNA but Watson and Crick were the first to fully understand and publish the model. -
Linus Pauling
Country: United States
Contribution: Pauling devised a model for proteins, but more importantly he determined the number of amino acids per turn of the alpa helix he devised as the shape of a protein. -
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