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370 BCE
Definition of Atom
Democritus defines an atom as the smallest unit of matter which still retains the identity and properties of that matter -
322 BCE
Refutation of Democritus
Aristotle refuted Democritus' Atomic Theory, leading many others to do so as well. -
Period: 300 BCE to
Alchemy
Greek philosophers became interested in Egyptian religion.
Alchemists start believing alchemy can lead to immortality. -
600
Spread of Alchemy
Arabs occupy Egypt and further develop alchemy and spread it to the west. Classification of metals begins. -
1500
Separation of Alchemy
European scientists separate alchemy into two groups. In the west, they focus on compounds, reactions, and chemical reactions. They invent distillation, percolation, extraction, and rudimentary chromatography.
The second group focuses on the spiritual, metaphysical side, and continue searching for immortality. -
The Phlogiston Theory
Johann Joachim Becher postulates a fire-like element called "phlogiston". It was said to be inside combustible bodies and released during combustion. Carbon dioxide was considered "dephlogisticated air". -
Period: to
The Father of Modern Chemistry
Anton Laurent de La Voisier is born. He relied on quantitative observation to develop conclusions. He also disproves the Phlogiston Theory by proving that oxygen is what makes things combust. He even discovers the Law of Conservation of Mass by proving the mass of a metal oxide equals the mass of of the same metal plus oxygen when the metal oxide decomposes. He discovers that matter can change form, but can't be created or destroyed during a reaction. He is beheaded in the French Revolution. -
Benjamin Franklin
He discovered that there are two electrical charges, positive and negative. The opposites attract, and the same charges repel. -
Period: to
The Creation and Experimentation of the CRT
The CRT (cathode ray tube) was created by William Crookes. It was a glass tube coated in fluorescent paint that would glow when connected to a battery. When a paddle wheel was connected to the CRT and the CRT was connected to a battery, the wheel would spin. This proved that since there was no other force inside the tube to spin the wheel, cathode rays had mass. Sir John Joseph Thompson continued to experiment on the CRT. -
The Law of Definite Proportions
Discovered by Joseph Louis Proust, it states that a chemical compound always contains exactly the same proportion of elements by mass. -
Period: to
The Father of Atomic Theory
John Dalton
His atomic theory:
1. Matter is made up of atoms that indivisible and indestructible.
2. All atoms of an element are identical (false).
3. -
Vitalism
People begin to believe in vitalism, the belief that living organisms are different from non-living entities because they have a "vital spirit". Therefore, living and non-living entities have different principles. -
Sir John Joseph Thompson
Thompson continued experimenting on the CRT. He used charged plates to deflect the cathode ray, and found that the ray would deflected away from the negative plate and towards the positive. He used this discovery to conclude that cathode ray was made of negative particles, which he named "electrons". -
Period: to
Ernest Rutherford
He classified radiation. He also found that atoms must be mostly empty space, they must have a solid core, and said core must be positively charged. He did this by painting the inside of a tin can with fluorescent paint and spreading a sheet of gold over the can. He then shined an alpha ray through the gold sheet. -
Becquerel
Becquerel discovered radioactivity in Uranium ore. -
The Curies
They discovered and isolated polonium and radium from uranium ores. They even had an element named after them (Curium). -
Millikan
Millikan calculated the mass and charge of the electron. -
James Chadwick
He proved the existence of another subatomic particle that had no charge. He named it the "neutron".