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Egyptians formulate the theory of the Ogdoad, or the "primordial forces", from which all was formed. These were the elements of chaos, numbered in eight, that existed before the creation of the sun
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Tapputi-Belatikallim, a perfume-maker and early chemist, was mentioned in a cuneiform tablet in Mesopotamia
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Empedocles asserts that all things are composed of four primal elements: earth, air, fire, and water, whereby two active and opposing forces, love and hate, or affinity and antipathy, act upon these elements, combining and separating them into infinitely varied forms
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Leucippus and Democritus propose the idea of the atom, an indivisible particle that all matter is made of. This idea is largely rejected by natural philosophers
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Plato coins term ‘elements’ (stoicheia) and in his dialogue Timaeus, which includes a discussion of the composition of inorganic and organic bodies and is a rudimentary treatise on chemistry, assumes that the minute particle of each element had a special geometric shape: tetrahedron (fire), octahedron (air), icosahedron (water), and cube (earth)
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Aristotle, expanding on Empedocles, proposes idea of a substance as a combination of matter and form. Describes theory of the Five Elements, fire, water, earth, air, and aether. This theory is largely accepted throughout the western world for over 1000 years
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First known records of Hermes in Byblos circa 60-141 AD. Hermes Trismegistus the 'thrice great' was a great figure of knowledge and through his teachings laid the foundations for hermeticism, which would later give birth to alchemy.
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Zosimos of Panopolis writes some of the oldest known books on alchemy, which he defines as the study of the composition of waters, movement, growth, embodying and disembodying, drawing the spirits from bodies and bonding the spirits within bodies
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Abu Musa Jabir ibn Hayyan (aka Geber), an Arab/Persian alchemist who is considered by many to be the father of chemistry, develops an early experimental method for chemistry, and isolates numerous acids, including hydrochloric acid, nitric acid, citric acid, acetic acid, tartaric acid, and aqua regia.
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Abū al-Rayhān al-Bīrūnī and Avicenna, both Persian chemists, refute the practice of alchemy and the theory of the transmutation of metals
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Magister Salernus of the School of Salerno makes the first references to the distillation of wine.
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Roger Bacon publishes Opus Maius, which among other things, proposes an early form of the scientific method, and contains results of his experiments with gunpowder.
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Andreas Libavius publishes Alchemia, a prototype chemistry textbook
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Sir Francis Bacon publishes The Proficience and Advancement of Learning, which contains a description of what would later be known as the scientific method
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Posthumous publication of the book Ortus medicinae by Jan Baptist van Helmont, which is cited by some as a major transitional work between alchemy and chemistry, and as an important influence on Robert Boyle. The book contains the results of numerous experiments and establishes an early version of the law of conservation of mass
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Robert Boyle publishes The Sceptical Chymist, a treatise on the distinction between chemistry and alchemy. It contains some of the earliest modern ideas of atoms, molecules, and chemical reaction, and marks the beginning of the history of modern chemistry. He also proposes Boyle's law, an experimentally based description of the behavior of gases, specifically the relationship between pressure and volume.
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Antoine Lavoisier, considered "The father of modern chemistry", recognizes and names oxygen, and recognizes its importance and role in combustion
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Jacques Charles proposes Charles's law, a corollary of Boyle's law, describes relationship between temperature and volume of a gas
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John Dalton proposes Dalton's law, which describes relationship between the components in a mixture of gases and the relative pressure each contributes to that of the overall mixture
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Amedeo Avogadro proposes Avogadro's law, that equal volumes of gases under constant temperature and pressure contain equal number of molecules
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Germain Hess proposes Hess's law, an early statement of the law of conservation of energy, which establishes that energy changes in a chemical process depend only on the states of the starting and product materials and not on the specific pathway taken between the two states
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Dmitri Mendeleev publishes the first modern periodic table, with the 66 known elements organized by atomic weights. The strength of his table was its ability to accurately predict the properties of as-yet unknown elements
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William Ramsay discovers the noble gases, which fill a large and unexpected gap in the periodic table and led to models of chemical bonding
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Niels Bohr introduces concepts of quantum mechanics to atomic structure by proposing what is now known as the Bohr model of the atom, where electrons exist only in strictly defined orbitals.
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Henry Moseley, working from Van den Broek's earlier idea, introduces concept of atomic number to fix inadequacies of Mendeleev's periodic table, which had been based on atomic weight
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Erwin Schrödinger described electrons as continuous clouds. Introduced 'wave mechanics' to mathematically describe the atom.