Atomic Theory Timeline

Topics: Atom, Ernest Rutherford, Chemistry Pages: 4 (430 words) Published: May 5, 2013
1869, Dmitri Mendeleev

• Used cards to arrange the elements and created the first periodic table.

Late 1890s, Joseph John Thompson

• Discovered electrons using cathode ray test tube experiments

• “Plum pudding” model of atoms (1900)– negative electrons in a positive framework

1800, John Dalton, English chemist:

• Proposed the atomic patterns, which account for the law of conservation of mass and the law of constant composition

• All matter is made of atoms; atoms of an element are identical; each element has different atoms; atoms of different elements combine in constant ratios to form compounds; atoms are rearranged in reactions.

• “Billiard ball’ model – atoms are solid and indivisible


500 B.C Greek philosophes
• everything belongs to a single unity
• Change & motion was an allusion

• Change & motion does exist,
• All nature existed as different object moving in a “void”.

1913, Niels Bohr

• Electrons orbit the nucleus in “shells” (electron configurations)

• Electrons can be bumped up to a higher shell if hit by an electron or a photon of light.

• Purposed the Bohr’s model & Bohr –Rutherford diagrams

1790, Joseph Priestly

• The first person who isolated elemental oxygen

Antoine Lavoisier

• Isolated and named Oxygen and Hydrogen

• Discovered the law of conservation of mass (atoms are neither created/destroyed) & the law of constant proportions (elements combine in fixed ratios)

• Wrote the 1st chemistry book (1789) , listed 33 elements

• Grouped the elements

350 B.C, Aristotle
• Modified matter was made of the “4 elements” though the experiment “the burning of wood”.



1661, Robert Boyle, Alchemist

• The first person who defined an element

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