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Development of the Atomic Theory

Development of the Atomic Theory. From Democritus to Dalton. Democritus. Greek philosopher 400 BC All matter is made up of atoms Atoms are solid and indestructible Atomos = ‘ indivisible ’ No experiments to support idea. The Atom.

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Development of the Atomic Theory

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  1. Development of the Atomic Theory From Democritus to Dalton

  2. Democritus • Greek philosopher • 400 BC • All matter is made up of atoms • Atoms are solid and indestructible • Atomos = ‘indivisible’ • No experiments to support idea

  3. The Atom • The smallest particle of an element that retains the properties of that element • Basic building block of matter

  4. Learning Check #1 • What does the word indivisible mean? • What is an atom? • Who first proposed the idea of atoms? • The smallest particle of an element that retains the properties of that element • Cannot be split! • Democritus

  5. Antoine Laviosier (1774) • Developed the Law of Conservation of Mass • Matter, like energy, is neither created nor destroyed in an ordinary chemical reaction • “One may take it for granted that in every reaction there is an equal quantity of matter before and after.”

  6. Joseph Proust • Developed Law of Definite Proportions • Any given compound always contains the same elements in the same proportions by mass. • Example – Water is always 88.9% oxygen and 11.1% hydrogen by mass

  7. Learning Check #2 • In a chemical reaction if I start with 100 g of material, how many grams should be there at the end? • In a compound, what do we know about the ratio of elements? • Who developed the Law of Conservation of Mass? • 100 g • Always the same! • Antoine Lavoisier

  8. John Dalton (1803) • English school teacher • Developed the first atomic theory. • First attempt, using experimentation, to prove the existence of atoms and explain the structure of matter

  9. Four Parts of Atomic Theory • All matter is composed of tiny indivisible particles called atoms. • All atoms of the same element are identical but are different from atoms of other elements. • A chemical compound always contains the same atoms in the same ratio. • In chemical reactions, atoms from one or more compounds or elements rearrange to form one or more new compounds. New elements are not formed.

  10. Learning Check #3 • According to Dalton, all matter is made up of? • Are all atoms of silver the same? What part of Dalton’s theory supports your answer? • Are new elements formed in a chemical reaction? • Indivisible atoms • Yes. Part #2. • No.

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