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385 BCE
-----Key-----
The events marked with "period" followed by a date indicate that the discovery the scientist contributed happened over the course of many years. It would be too difficult to narrow down to a single instance within the date. Otherwise, the events are marked with a date on top, that indicates the result of a specific discovery, then followed by the scientists' name and the years they were alive. Finally, concluded by a description of the discovery. Format:
XXXX Name (years alive)
Description -
Period: 384 BCE to 322 BCE
Aristotle
Aristotle argued everything was in balance, and made from four elements: earth, air, fire, and water. These four elements were also in different states: hot and dry, or cold and wet. -
Period: 460 to 370
Democritus
Contrary to Aristotle's statement, Democritus proposed all material substance was made of tiny particles called atomos. -
1242
Roger Bacon (1214-1294)
Roger Bacon becomes the first person to describe in detail the process of making gunpowder and the explosive properties of it. -
Sir Francis Bacon (1526-1626)
Sir Francis Bacon said that inductive logic is to be preferred over deductive logic for naturalistic study because it can allow for a conclusion to be false. -
Period: to
Robert Boyle
Mr. Boyle pointed out doubt was important in experimentation, he wrote "The Skeptical Chymist", and proposed there are more than four elements. -
Period: to
Antoine Lavoisier
Known as the "Father of Modern Chemistry," Lavoisier performed systematic experiments discovering the law of the conservation of mass. He also made the first chemistry textbook (1789). -
Period: to
Lavoisier and Liebig
Multiple chemists including Antoine Lavoisier and Justus von Liebig discovered ways to determine the amount of carbon, oxygen, and nitrogen in chemical compounds. They often used complicated methods relying on combustion and the law of the conservation of mass. -
Alessandro Volta (1745-1827)
Volta created the first battery in the form of the voltaic pile, one of the first reliable sources of electricity. -
John Dalton (1766-1844)
Considering previously determined laws such as the law of definite proportions and the law of multiple proportions, Dalton proposed an atomic theory with 5 main points. However, some of them were disproved later. -
Joseph Proust (1871-1922)
Proust summarized his studies in the years prior by making Proust’s Law (the law of definite proportions), stating that chemical formulas are formed of constant, defined ratios. -
Dmitri Mendeleev (1834-1907)
Mendeleev was known for making the first periodic table of elements, discovering a pattern prior to its creation. The table was first organized by mass then affinity along with a few other factors. -
Eugen Goldstein (1850-1930)
Goldstein discovered atoms have a positively charged and negatively charged potential while working with a Crookes tube and magnetism. -
Henri Becquerel (1852-1908)
While investigating the newly invented X-rays, Becquerel accidentally stumbled upon properties or uranium salts penetrating a photographic plate, thus discovering radioactivity. -
Sir Joseph John (JJ) Thomson (1856-1940)
Using a cathode ray tube, JJ Thomson discovered every atom was made of smaller, negatively charged particles that were eventually called electrons. He proposed the plum pudding model to show what he saw. -
Robert Millikan (1868-1953)
He was known for discovering the amount of electrical charge in an electron as well as the mass. The mass was about 1/1187 of a hydrogen atom. -
Period: to
Ernest Rutherford (1871-1937)
Using the gold foil experiment, he discovered the atom was mostly empty space with a dense core, therefore making a more accurate model of the atom. He also theorized about a positively charged particle inside an atom, but was unable to prove it. -
Henry Moseley (1871-1915)
Moseley created the atomic number, which indicated the amount of protons inside the atom and became the primary sorter for the periodic table. -
Period: to
James Chadwick (1891-1974)
Chadwick discovered the neutron inside the nucleus of an atom by bombarding Beryllium atoms with alpha radiation.