unit 1: atomic structure ap chemistry evolution of atomic theory
TRANSCRIPT
Unit 1: Atomic StructureAP Chemistry
Evolution of Atomic Theory
Democritus – 400 B.C.
Greek Philosopher Imagined particles
that were indivisible
Constituents of matter
Atom comes from “atomos”
Opposed Aristotle
Aristotle – 350 B.C.
Widely accepted theory that all matter can be continually divided.
Set science back for thousands of years.
Alchemy
A pseudoscience that superceded scientific discoveries.
Alchemists attempted to turn metals into gold and developing the “elixir” of life (able to cause immortality and create life).
Pierre Gassendi - 1650
Reintroduced Particulate theory
No experimental evidence
Supported by Sir Isaac Newton
Robert Boyle - 1661
Studied Gases 1st to use the term
element in its current context in his book The Skeptical Chemist
George Stahl - 1717
Suggested “phlogiston” flowed from burning material
A necessary ingredient of combustible material
Joseph Priestly - 1774
discovered oxygen supports combustion
Antoine Lavoisier - 1778
Developed Law of Conservation of Mass
Explained combustion
Joseph Proust - 1799
Developed “Proust’s Law” using copper oxide
Later renamed, the Law of Definite Proportions
Nearly discovered the Law of multiple proportions, but his data used percentages instead of weights.
John Dalton - 1802
First to develop an atomic theory. It has 4 postulates. Each element is made
up of atoms Atoms of the same
element are identical in mass and properties. Atoms of different elements differ in some way.
John Dalton - 1802
Compounds are made when atoms combine. If elements combine in more than one whole number ratio, the resulting compound has different properties
Chemical reactions involve the reorganization of atoms.
Amedeo Avogadro - 1811
Developed Avogadro’s Law. Equal volumes of gases have equal number of molecules at constant temperature and pressure.
Expanded Dalton’s concept of atomic masses
J.J. Berzelius - 1813
Established the 1st system of using letters to represent elements.
William Prout - 1815
Proposed that Hydrogen was the fundamental material that all other elements were made from. All atomic masses were multiples of the mass of hydrogen.
Michael Faraday - 1833
Found Faraday’s Constant. 1 mole of e- = 96500 coulombs.
Alexandre Béguyer de Chancourtois - 1862
1st periodic arrangement of elements.
Divided surface of a cylindrical base into 16 segments because oxygen has a mass of 16.
John Newland - 1863
Developed the law of octaves Properties of
elements repeat every eighth element.
Dimitri Mendeleev - 1869
Classification based on chemical properties.
Considered the first periodic table.
Left gaps for missing elements and predicted their properties
William Crookes - 1879
Showed that cathode rays stream from the negative pole
Eugene Goldstein - 1886
Discovered the proton using a cathode ray tube.
William Roentgen - 1895
Discovered x-rays. Rays were
penetrating and of short wavelength
Henri Becquerel - 1896
Discovered radioactivity.
Used uranium salts
Marie Curie - 1897
Student of Becquerel
Showed that radioactivity is atomic property
Isolated radium and polonium
J.J. Thomson - 1897
Determined the mass/charge ratio of the electron.
5.69 x 10-9
Used the cathode ray tube
Proposed a model of the atom that was mockingly called the “plum pudding” model
Robert Millikan - 1909
Determined the charge of the electron using the famous oil-drop experiment
1.60 x 10-19
From this and Thomson’s value, the mass was calculated to be 9.11 x 10-28g
Ernest Rutherford - 1911
Performed the famous gold foil experiment
Determined 3 things The atom is mostly
empty space The nucleus is
positively charged The nucleus is a
small dense part of the atom
Gold Foil Experiment
Gold Foil Experiment
Henry Moseley - 1913
Calculated atomic number by determining the nuclear charge of an atom.
Niels Bohr - 1913
Observed spectral lines for hydrogen
Proposed an orbit theory of the electron around the atom.
Bohr Model
Hydrogen Spectrum
Gilbert Lewis - 1916
Suggested that noble gases have 8 valence electrons
Atoms will gain or lose electrons to achieve 8 outer electrons.
Louis De broglie - 1924
Suggested that matter could exhibit wave properties
Observed diffraction patterns in electrons
Wolfgang Pauli - 1924
Pauli Exclusion Principle – 2 electrons cannot have the same 4 quantum numbers
Erwin Schrödinger - 1926
Developed a wave equation.
Mathematical function that described the nature of the electron
James Chadwick - 1932
Discovered the neutron
Other Contributions
C.D. Anderson – 1932 Discovered the positron
Enrico Fermi – 1940 Prepared more than 40 radioactive
elements