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400 BCE
Democritus
Country of origin: Greece
Observations/experiments/evidence: was mentored by Leucippus, who had originally come up with the idea, which was adopted by Democritus.
Discovery: developed concept of the atom making up everything in the universe and the atomic theory.
Contribution: introduced the atom to the scientific world that blossomed and inspired others over centuries. -
300 BCE
Aristotle
Country of origin: Greece
Observations/experiments/evidence: wrote books and essays on philosophy and meteorology, studied the sciences
Discovery: hypothesized that all matter is composed of combinations of earth, wind, fire and water
Contribution: Did not believe the atomic theory and pushed further pursuit in that area off by 200 years, but did develop the scientific method. -
700
Abu Musa Jabir ibn Hayyan
Country of origin: Iran
Observations/experiments/evidence: the balance of natural factors always fell proportionately to a ratio of 1:3:5:8, adding up to 17 or a multiple of 17.
Discovery: Developed a system of arithmology referred to as "the method of balance". It helped to determine the four natural states of the universe (hot, cold, wet, dry), by distributing numerical value to each Arabic letter of it's name.
Contribution: Went hand in hand with Aristotle's theory of matter. -
1250
Albert Magnus
Country of origin: Germany
Observations/experiments/evidence: Performed an experiment to obtained the toxic properties found in the mined compounds by heating soap together with orpiment (arsenic trisulphide, As2S3).
Discovery: Discovered Arsenic
Contribution: Added an element to the periodic table -
Robert Boyle
Country of origin:
Observation: Wrote a book disagreeing with the concepts brought up by Aristotle
Discovery: Replaced old ideas with a new modern idea of the atom, and that it cannot be separated into simpler components.
Contribution: Re-birthed the concepts of atoms making up everything in the universe. -
Henry Cavendish
Country of origin: France
Observation: researched the composition of atmospheric air and the properties of different gases
Discovery: Realized hydrogen gas had distinct atomic properties
Contribution: He was the first to recognize hydrogen gas as a distinct substance for which he calculated their densities as well as the densities of several other gases. -
Antoine Lavoisier
Country of origin: France
Observation: Used a balance to find sound and accurate mass measurements.
Discovery: helped construct the metric system, added a plethora of new elements to the list, and was able to get closer to the masses of certain pure elements.
Contribution: His results led to one of the fundamental laws of chemical behavior: the law of conservation of matter, which states that matter is conserved in a chemical reaction. -
John Dalton
Country of origin: United Kingdom
Observation: Saw structure and guidelines that atoms seems to follow throughout his experiments.
Discovery: proposed a modern theory of the atom based on some basic assumptions of atoms.Created the first chart of atomic weights
Contribution: proposed modern atomic theory. -
Amedeo Avagadro
Country of origin: Italy
Observation: under controlled conditions of temperature and pressure, equal volumes of gases contain an equal number of molecules.
Discovery: Avogadro's law
Contribution: Most noted contribution to molecular theory now known as Avogadro's law, which states that equal volumes of gases under the same conditions of temperature and pressure will contain equal numbers of molecules -
Dmitri Mendeleev
Country of origin: Russia
Observation: The known elements of the time followed a pattern of mass and certain data, he wanted a more organized way to view it.
Discovery: Created a version of the periodic table sorted by relative atomic mass
Contribution: Was able to predict the existence of properties that we hadn't yet discovered, whose spaces we are still filling in today. -
Marie Curie
Country of origin: Poland
Observation:
Discovery: developed theory of radioactivity, techniques for separating radioactive isotopes, and discovered two new elements: polonium and radium.
Contribution: discovery of new elements and progression of woman scientists. -
J.J. Thompson
Country of origin: United Kingdom
Observation: performed a series of experiments in 1897 designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, an area being investigated by many scientists at the time
Discovery: electron, isotope, subatomic particle
Contribution: proved there were smaller things in the universe than just atoms -
Niels Bohr
Country of origin: Denmark
Observation: Researched and studied the structure and radioactivity of the atom
Discovery: the atom is a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus
Contribution: proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities -
Ernest Rutherford
Country or origin: New Zealand
Observation: used the gold foil experiment to show that atoms had nuclei
Discovery: the proton, he conducted research that led to the first "splitting" of the atom in 1917.
Contribution: showed that there is a more complex structure to the atom with the Rutherford model -
Heisenberg
Country of origin: Germany
Observation: worked on the Manhattan project with Niels Bohr, thought that the observation of a subject would induce change
Discovery: Uncertainty principle
Contribution: Use of uncertainty principle and theories of quantum mechanics -
Erwin Schrodinger
Country of origin: Austria
Observation: noted theoretical physicist and scholar who came up with a groundbreaking wave equation for electron movements
Discovery: developed a powerful model of the atom
Contribution: it revolutionized quantum mechanics and earned Schrödinger a share in the 1933 Nobel Prize in Physics. -
James Chadwick
Country of origin: United Kingdom
Observation: He bombarded beryllium atoms with alpha particles. An unknown radiation was produced. This particle became known as the neutron.
Discovery: Discovered the neutron
Contribution: changed the idea that atoms were a positively charged nucleus surrounded by negative particles -
Lise Meitner
Country of origin: Austria
Observation: Studied radioactivity and nuclear physics
Discovery: collaborated in the discovery of nuclear fission and gave the first theoretical explanation of the fission process.
Contribution: one of the most important women of the 20th century -
Rosalind Franklin
Country of origin: United kingdom
Observation: DNA molecule shaped like a twisted ladder
Discovery: contributed to the discovery of the double-helix structure of DNA
Contribution: contributed to the understanding of the fine molecular structures of DNA, RNA, viruses, coal and graphite -
Linus Pauling
Country of origin: United States
Observation: saw the structure of crystals using X-ray crystallography
Discovery: Combined with math calculations, formed Pauling rules for atomic structure of crystals with Ionic bonding
Contribution: enabled him and others to more accurately predict and determine crystal structures