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400 BCE
The idea of the atom, proposed by Democritus
The Ancient Greek Philosopher, Democritus, developed the concept of the atom. The atom get it's name from the Greek word "atom" because is means "indivisible". He believed the atmosphere and universe were made up of microscopic particles at were indestructible. This idea lead to the later developed Atomic Theory. -
340 BCE
Aristotle and his Theory of the Elements
Aristotle, a Greek Philosopher, believed that that all the materials on Earth were not made of Atoms. He believed the materials were made by the "Elements of Matter". These four elements were Earth, Water, Air, and Fire. He developed the idea that all substances and materials were made up of small amounts and portions of these elements. -
762
Abu Musa Jabir idn Hayyanas
Abu Musa Jabir idn Hayyanas was known to many as "the father of Arab chemistry". He had many different titles including an Islamic alchemist, pharmacist, philosopher, astronomer, and physicist. It is still unclear when his discoveries on creating simple crystallization and distillation methods was, but it is estimated to be around 762. -
1250
Albert Magnus: Arsenic
Albert Magnus was a scientist from Germany. He is known today for his discovery of the element of Arsenic. He discovered this by heating soap and orpiment together. This discovery by Magnus lead to later discoveries of other elements. This furthered the possibility of combining elements to make matter. -
1440
The Printing Press
The Printing Press was originally invented in the Holy Roman Empire by the German Johannes Gutenberg. Before the printing press, most European texts were printed using Xylography, a form of woodblock printing. This invention, known as the movable type, is considered the most important invention in history. The printing Press allowed for information to be spread quickly and accurately. This also made the public more literate. -
The Vacuum Tube and Electric Generator
Otto von Guericke was a scientist from Germany. He is known today for his invention of the Vacuum Tube and the Electric Generator. His studies and research later led to an increasing number of studies on air particles and air pressure. -
Robert Boyle's Law Formation
Angle-Irish philosopher, Robert Boyle was a very accomplished man. He was a chemist, a physicist, and an inventor. Boyle's Law (pv = k) was discovered when Boyle realized the pressure of a given quantity of gas is the inverse, or opposite, of it's volume at a constant temperature. -
The Precision Balance
Though historians do not know the official date or inventor, they believe the Precision Balance was invented sometime around 1700. The precision balance was invented by early Egyptians. It can also be called the analytical balance. This balance is continually used in modern chemistry to this day. -
Henry Cavendish: Discovery of Hydrogen
Henry Cavendish was a British philosopher, chemist, and physicist. He was the first scientist to recognize hydrogen gas as a distinctive substance. He described the density of hydrogen, which he called "inflammable air". He did extensive research on the makeup atmospheric air. He also described the makeup of of water and made the first accurate measurement of the density of the Earth. -
Antoine Lavoisier: the Law of Conservation of Mass
French Chemist Anthony Lavoisier is known for the establishment of the Law of Conservation of Mass in November of 1787. The Law of Conservation of Mass states: Mass is neither created or destroyed in a chemical reaction. He also proposed the Combustion Theory after conducting a careful study on the burning process. This theory was based on the sound mass measurements. He is known for sparking the question for many scientists on what an atom actually is. -
John Dalton and his Atomic Theory
John Dalton was an English chemist, physicist, and meteorologist with a Quaker background. John Dalton was the first to describe the atom as a solid chemical object. John Dalton's atomic theory is made up of multiple pieces including: All matter is made up of atoms, all atoms of a given element are identical in mass and properties, compounds are formed from multiple atoms, and a chemical reaction is a rearrangement of atoms. This theory is still accepted today. -
Avogodro's Hypothesis
Amedeo Avogodro was an Italian mathematical physicist. He is mostly known for his contribution to the molecular theory now known as Avogodro's law. This law states that equal volumes of gases under the same conditions of temperature and pressure will contain equal numbers of molecules. The hypothesis was regreated by other scientists and was not widely accepted until after his death. This hypothesis allows scientists to predict the behavior of ideal gasses. -
Mendeleev and his Periodic Table
Dimitri Ivanovich Mendeleev was a Russian chemist and inventor. Mendeleev is best known for his discovery of the periodic law and for his formulation of the periodic table of elements. He arranged the elements known at the time in order of relative atomic mass, and also did other things which made his table very famous then and today. He stated that if the elements were put in order of the atomic mass, then certain sets of properties would recur periodically. -
JJ Thomson: Discovery of the Electron
Sir Joseph John Thomson was an English physicist. Thomson discovered the electron by experimenting with a Crookes tube. He demonstrated that the cathode rays were negatively charged. He also experimented with positively charged particles in Neon Gas. His discovery and identification of the electron and the discovery of the first subatomic particle helped to revolutionize the knowledge of the atomic structure. -
Marie and Pierre Curie: Discovered Elements
Marie Curie was a Polish physicist and chemist. Pierre Curie was a French physicist. the Curies are best known for their pioneering work in the study of radioactivity, which led to their discovery of the elements radium and polonium. The work of Marie and Pierre Curie led to the way toward the modern understanding of the atom as an entity that can be split to release enormous energy. -
Sir William Ramsey: Noble Gases
Sir William Ramsey was a British chemist. He discovered five new elements, called the Noble Gases, including Helium, Neon, Argon and Krypton. This whole new group of elements called Noble Gases do not react with anything. This is why they are also called inert gases. He received the Noble Prize in 1904 "in recognition of his services in the discovery of the inert gaseous elements in the air. -
Ernest Rutherford: Rutherford's Model
Ernest Rutherford was a British physicist who became famous in the study of nuclear physics. He was responsible for remarkable discoveries in radioactivity and nuclear physics. One of his most important discoveries was identifying alpha particles as helium nuclei. Rutherford's model of the atom is known for the region called the Nucleus of the atom. He also set forth the laws of radioactive decay. -
Niels Bohr: Structure of Atoms
Danish physicist, Niels Bohr, contributed to understanding the atomic structure and quantum theory. He won a Noble Prize on his research on the structure of the Atom. Bohr proposed a theory for the hydrogen atom based on the quantum theory that energy is transferred only in certain well defined quantities. The Bohr model the atom as a small, positively charged nucleus, surrounded by electrons travelling in circular motion around the nucleus. -
Louis de Broglie: Wave Characteristics
Louis de Broglie was a French physicist who made groundbreaking discoveries and contributions for the quantum theory. He speculated that nature did not single out light as being the only matter which exhibits a wave-like motion. He proposed ordinary particles, such as electrons, protons, etc could exhibit wave characteristics in certain circumstances. He was awarded the Noble Prize in Physics in 1929 -
Heisenberg: Theory of Quantum Mechanics
German physicist and philosopher, Heisenberg, is most famous for his Theory of Quantum Mechanics. The Theory of Quantum Mechanics compared the smallest scales of energy levels in atoms and subatomic particles. This theory later led to the discovery of allotropic forms of hydrogen. -
Erwin Schrodinger: Wave Equation
Erwin Schrodinger was an Australian physicist who developed a number of fundamental results in the field of quantum theory, which formed the basis of wave mechanics. He formulated the wave equation, which is the description of how waves work in classical physics. Examples of these would be sound waves, light waves, and even water waves. He was awarded the 1933 Noble Prize in Physics. -
Chadwick's discovery of Neutrons
James Chadwick, an English Physicist awarded for the Noble Prize, discovered the idea that Neutrons are located in the center of an atom, along with the Protons. Neutrons match their name in the sense that they are neutral: they don't have a positive or negative charge. They do contribute to the atomic weight of an atom, having the same effect as a proton. -
Lise Meitner: Nuclear Fission
Lise Meitner was an Austrian-Swedish physicist who focused specifically on radioactivity and nuclear physics. She worked with a small group of scientists to discover that a uranium atom would split when it was bombarded by neutrons. She proved splitting a uranium atom was possible, this being where the term Nuclear Fission came to be. Many consider he to be one of the most important women scientists of the 20th century. -
Irene Joliot-Curie: Artificial Radioactivity
Irene Joliot-Curie, daughter of Marie and Pierre Curie and wife of Fredrec Joliot-Curie, was a French scientist. She served as a nurse radiographer during the first World War. Irene Joliot-Curie won a Noble Prize in 1935 for the discovery, with her husband, of artificial radioactivity. They recognized and synthesized new radioactive elements. -
Linus Pauling
Linus Pauling was an American chemist and biochemist. He is known was the 20th century's greatest chemist for his research on the nature of the chemical bond and how it effects the structure of complex substances. Pauling discovered the spiraling structure of proteins. This later lead to the discovery and breakthrough of Watson and Crick's DNA Double Helix. -
Rosalind Franklin: Shape of DNA
Rosalind Franklin was an English Chemist who made contributions to the understanding of the molecular structures of DNA, RNA, viruses, coal, and graphite. Franklin contributed to the discovery of Watson and Crick, stating that DNA was shaped as a twisted ladder. It is known today that Photo 51, the picture Watson, Crick, and Wilkins used to discover and win the Noble Prize for, was actually made by Franklin. When the three scientists won the Noble Prize, they wrote about Franklin as a villain.
