General Chronological Categories of Chemistry

Due to the amount of time chemistry takes up on the timeline, the science is split into four general chronological categories. The four categories are: prehistoric times -, (alchemy), (traditional chemistry) and (modern chemistry).

PRE-HISTORIC TIME  (beginning of the Christian era):

-Known metals were recorded and listed in conjunction with heavenly bodies.

-Democritus proclaims the atom to be the simplest unit of matter. All matter was composed of atoms

-Aristotle declares the existence of only four elements: fire, air, water and earth. All matter is made up of these four elements and matter had four properties: hot, cold, dry and wet.

ALCHEMY (beginning of the Christian era - end of 17th century)

-Influenced greatly by Aristotle's ideas, alchemists attempted to transmute cheap metals to gold. The substance used for this conversion was called the Philosopher's Stone.

- Alchemists not only wanted to convert metals to gold, but they also wanted to find a chemical concoction that would enable people to live longer and cure all ailments. This elixir of life never happened either.

TRADITIONAL CHEMISTRY (end of 17th century - mid 19th century)

-John Dalton publishes his Atomic Theory which states that all matter is composed of atoms, which are small and indivisible.

-Joseph Priestley heated calx of mercury, collected the colorless gas and burned different substances in this colorless gas. Priestley called the gas "dephlogisticated air", but it was actually oxygen. It was Antoine Lavoisier who disproved the Phlogiston Theory. He renamed the "dephlogisticated air" oxygen when he realized that the oxygen was the part of air that combines with substances as they burn. Because of Lavoisier's work, Lavoisier is now called the "Father of Modern Chemistry"

MODERNY CHEMISTRY (mid 19th century – present)

-Was created the first vacuum tube by Heinrich Geissler

- Eugene Goldstein discovered positive particles by using a tube filled with hydrogen gas (this tube was similar to Thomson's tube...see 1897). The positive particle had a charge equal and opposite to the electron. It also had a mass of 1.66E-24 grams or one atomic mass unit. The positive particle was named the proton.

- Robert Millikan discovered the mass of an electron by introducing charged oil droplets into an electrically charged field. The charge of the electron was found to be 1.602E-19 coulombs. Using Thomson's mass ration, Millikan found the mass of one electron to be 9.11E-28 grams. Millikan received the 1932 Nobel Prize in Physics for this discovery.

- The neutron was founded by James Chadwick