Atomic structure

Development of the Atomic Theory

By nguyentham

  • Alchemists

    Alchemists
    • Alchemists (16th & 17th century – 1500’s & 1600’s) worked by trial and error – search for ‘panacea’ [pan-uh-see-uh], cure for all ailments (: a slight illness).
     Believed in discovering the ‘alkahest’ [al-kuh-hest], a universal solvent.
    • Understanding of processes (i.e. production of iron, etc.) was limited - known to work but unknown how or why.
    • Advance in large-scale production of fine-quality steel relied on Henry Bessemer’s (1813-1898, English engineer, inventor & Business man) underst

  • Robert Boyle

    Robert Boyle
    • English scientist:  1st to define an element. “…not being made of any other bodies or of one another”  As a simple substance and of compounds as being formed from a combination of elements.

  • Joseph Priestley

    Joseph Priestley
    • (1733-1804) – an English chemist
     1774: isolated O2 (element oxide), by collecting the gas produced when re mercury (II) oxide (HgO)is decomposed by heating.
     Nicknamed ‘Doctor Phlogiston’ because of unshakable (& incorrect) belief that combustible materials contained a mysterious substance named ‘Phlogiston’.

  • The Fisrt Fleet arrives in Australia

    The Fisrt Fleet arrives in Australia
    "The ships arrived at Botany Bay between 18 and 20 January 1788"

  • John Dalton

    John Dalton
    • (1766- 1844): English chemist and Physicist
     Devised symbols for elements & compounds from circles and letters of the alphabet
    Atomic Theory:
    • (solid balls of matter)
    • Proposed that: all matter/elements were composed of very small indivisible particles called atoms, which were characteristic of that element.
    • Atoms are indestructible – chemical reactions involve the rearrangement of atoms.
    • Atoms of different elements combine in simple numerical (whole-numbered) ratios to for

  • Jöns Jakob Berzelius

    Jöns Jakob Berzelius
     Highly regarded analytical chemist
     Prepared, purified and identified many chemical elements & hundreds of compound s
     Devised idea of using letters and symbols to stand for names of elements
     Calculated accurate relative atomic mass for many elements (published 1828)

  • The Crimean War

    The Crimean War
    (October 1853 – February 1856)

  • Dimitri Mendeleev

    Dimitri Mendeleev
    • (1834-1901) – Russian Chemist
    • Constructed the periodic table (1869) into
     Groups: similar chemical properties
     Periods: in order of increasing relative atomic mass (RAM)
    • Left gaps in his periodic table for elements yet to be discovered – predicted their properties with close accuracy.

  • Joseph John Thomson

    Joseph John Thomson
    • proposed that atoms are positively charged spheres with equal amount of negatively charged electrons embedded in them with a mass far smaller than individual atoms.
    • his model is known as the 'plum pudding model' (1904)
    • How did he come to this conclusion? --> with cathode ray experiments using different metals

  • Ernest Rutherford

    Ernest Rutherford
    Proposed:
    - the atom as mostly empty space with positively charged nucleus and electrons orbiting the nucleus.
    Most of the mass of an atom if ound in the centre of the atom (however, could not explain mass increase)
    - used the alpha particle experiment with gold
    - atom model known as the 'solar system model'

  • Niels Bohr

    Niels Bohr
    • atoms consist of a positive nuclues with electrons in certain orbits of fixed energy called 'shells'.
    • shelld closest to the nucleus had lowest energy. no. of protons = no. of electrons
    • as long as an electron remains in the orbit, it does not lose energy
    • if an elctron absorbs enough energy, it can jump from one energy level to a higher one.
    • experiments included the emission spectra of hydrogen --> electrons did not emit energy and spiral into the nucleus.
    • model: 'shell model'

  • World War I

    World War I
    "began on 28 July 1914 and lasted until 11 November 1918"

  • Erwin Schrodinger

    Erwin Schrodinger
    • obeserved electrons behaviour (electrons dod not spiral into the nucleus) Proposed:
    • electrons behave as negative clouds of charge found in regions of space called orbitals, and each shell has subshells (each with its own definite energy level)
    • move in orbitals rather than in fixed orbits
    • within each subshell there are orbitals, all of the same energy level
    • an orbital can hold no mpore than two electrons description of an atom is known as 'wave machanics' or 'quantum machanics'.

  • James Chadwick

    James Chadwick
    Proposed:
    - the nucleus containa positive protons AND neutral neutrons (this helped explian why isotopes differ)
    - also used a cathode ray to show that some particles dod not react to a magnet.
    - used alpha particle experiment with beryllium and the scattered particles produced had a neutral charge and an equal mass to a proton
    - chadwicks model is the latest model that modern society still uses

  • World War II

    World War II
    "1 September 1939 – 2 September 1945 (6 years, 1 day)"

  • Atomic bombings of Hiroshima and Nagasaki (Japan)

    Atomic bombings of Hiroshima and Nagasaki (Japan)
    6–9 August 1945

  • First Space Travel to the Moon

    First Space Travel to the Moon
    "Manned exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans."

  • Chernobyl Disaster

    Chernobyl Disaster
    "was a catastrophic nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine"

  • The Launch of the Hubble Space Telescope

    The Launch of the Hubble Space Telescope
    "a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation."
    It was launched at 8:33:51 am.