Atomic Theory :Atomic Theory A Short History


Leucippus (5th century BCE) :Leucippus (5th century BCE) Among the earliest originators of the idea of indivisible (un-cut-able) elements called atoms. He also stated the Law of Causality that says everything in the world has a natural cause.


Democritus (450 BCE) :Democritus (450 BCE) Student of Leucippus Co-originator of the belief that all matter is made up of indivisible elements called "atomos" (English word – atom) Impossible to tell which ideas were Democritus’ and which are Leucippus’


Democritus :Democritus Basic elements exist and can be rearranged into different forms Atoms only had several properties size, shape, and (perhaps) weight All other properties, such as color and taste, are the result of interactions between the atoms in our bodies and the atoms of the matter that we are examining


Democritus :Democritus The real properties of atoms determine the perceived properties of matter Something sharp - small, pointy atoms Something sweet - large, round atoms Atoms of solids - hooks to attach to each other Atoms of oils - small atoms that slip past each other


Aristotle (384 BCE – 322 BCE) :Aristotle (384 BCE – 322 BCE) student of Plato and teacher of Alexander the Great One of the most influential of ancient Greek philosophers Because he did not believe in a void, he reasoned that atoms could not exist If atoms are small, discrete particles, what is between them?


Epicurus (341 BCE – 270 BCE) :Epicurus (341 BCE – 270 BCE) Founder of Epicureanism Admitted women and slaves into his school Believed matter was made up of uncuttable little bits of matter (atoms) flying through empty space (void) Everything is the result of atoms interacting with one another


Lucretius (94 BCE - 49 BCE) :Lucretius (94 BCE - 49 BCE) Roman poet and philosopher Long poem “On the Nature of Things” He expounded the philosophy of Epicurus Everything can be explained by motions of tiny atoms and groups of atoms interacting in empty space


Middle Ages (400’s to 1400’s) :Middle Ages (400’s to 1400’s) Civilization suffered in Western Europe Roman knowledge became less known Arab culture thrived – Roman texts translated into Arabic, and returned to Europe during Renaissance Few people received schooling before 1000 Many artistic and technical skills were lost Our current University system was created Writers used stories and rumors as truth


Pierre Gassendi (1592 – 1655) :Pierre Gassendi (1592 – 1655) Urged the importance of experimental research Did not accept writings blindly Used empirical evidence to support the existance of a void Relied on historical models to support the existance of atoms


Robert Boyle (1627 – 1691) :Robert Boyle (1627 – 1691) first modern chemist Defined elements as we do Invented vacuum pump Created a vacuum and tested with sound Gave proof that the void existed Allows for idea of atoms


Antoine Lavosier 1743-1794 :Antoine Lavosier 1743-1794 Law of Conservation of Mass Helps invent metric system Dies on guillotine in French Revolution


Antoine Lavosier :Antoine Lavosier showed a compound is combusted in a closed system has no loss in mass leads to the Law of Conservation of Mass "mass can neither be created or destroyed in chemical reactions." The amount started is all there at end


Joseph Proust (1754-1826) :Joseph Proust (1754-1826) formulated the Law of Definite Proportions, "different samples of a pure chemical substance contain the same proportion of elements by mass." Analyzed copper carbonate Opposed by Berthole


Claude Louis Berthollet(1748 -1822) :Claude Louis Berthollet(1748 -1822) devised a chemical nomenclature system of names serves as the basis of the modern system of naming chemical compounds along with Antoine Lavoisier and others Amount of reactant effects proportions of compound


Proust vs. Berthollet :Proust vs. Berthollet Definite composition vs reactant amounts Debated their ideas Actual fist fight on stage once Resolved by experimental data Proust correct Berthollet goes on to study equilibrium Leads to mass-action