The Development of the Periodic Table

  • Birth of John Dalton

    Eagles-field, England UK
  • Birth of Johann Döbereiner

    Hof, Germany
  • Dalton's Atomic Theory

    Was the first attempt to describe all matter in terms of atoms and their properties. Based on the law of conservation of mass and the law of constant composition. The theory states that:
    - all matter and elements exist as atoms
    - atoms of a particular element are identical in mass and properties
    - atoms link or separate in a chemical reaction
    - atoms combine in whole number ratios to form compounds
    Due to the discovery of subatomic particles and isotopes, parts of the theory had to be modified
  • Law of Triads

    Johann Döbereiner noticed that some elements had similar properties and put forward the Law of Triads. Shows triads of elements with similar chemical properties and states that the properties of the middle element could be predicted from the properties of the other two elements
  • Birth of Dmitri Mendeleev

    Tobolsk, Russia
  • Birth of John Newlands

    Lambeth, England
  • Death of John Dalton

    Manchester, England
  • Death of Johann Döbereiner

    Jena, Germany
  • Birth of J.J Thomson

    Manchester, England
  • Atomic Mass

    At a conference in Karlsruhe, Germany a more accurate list of the atomic mass of the elements became available which made real progress towards the discovery of the modern periodic table
  • The Law of Octaves

    John Newlands noticed if elements were arranged in order of atomic weight, there was a periodic similarity after each interval of 7 elements. He arranged the first 20 elements in this order but a pattern couldn't be found for all the elements
  • Newland's Periodic Table

    John Newland's published a periodic table. By ordering according to his law of atomic mass, he was forced to put some elements into groups which did not match their chemical properties. As a result his table was not accepted by other scientists
  • Mendeleev's Periodic Table

    Mendeleev's Periodic Table is most similar to the one used today with elements placed in order of increasing atomic weight. He placed elements with similar properties underneath each other and left blanks for undiscovered elements. Unfortuantly the arrangement did not always match the position predicted by chemical properties but if it seemed to be in the wrong place due to this he simply moved it to match this pattern
  • Birth of Ernest Rutherford

    Brightwater, New Zealand
  • Birth of Neil's Bohr

    Copenhagen, Denmark
    Element 107 on the periodic table is named Bohrium in his honour
  • Birth of Henry Mosley

    Weymouth, Dorset, England
  • Birth of James Chadwick

    Bollington, England
  • Discovery of the Electron

    Thomson's reasearch of cathode rays concluded that they were not a form of radiation rather consisted of a stream of negatively charged particles with mass now known to be electrons. Thomson then went to propose a model for the structure of an atom. Thomson was able to estimate the mass of a cathode ray electrons and presented the conclusion that atoms must be divisible into smaller states of matter, contrary to Dalton's concept that an atom was a small, dense sphere with no internal structure
  • Death of John Newlands

    London, England
  • Thomson's Atomic Model

    Consisted of numerous very small negatively charged electrons imbedded within a larger uniform poisitively charged sphere. His model became known as 'plum-pudding' but was short lived due to the research conducted by Rutherford
  • Death of Dmirtri Mendeleev

    St. Petersburg, Russia
    Never received a Nobel Prize for his work but element 101 was named Mendelevium in his honour
  • Rutherford Model

    Rutherford proposed that atoms consisted mostly of empty space occupied by the very low mass negatively charged particles called electrons. These electrons orbited the centre of an atom - the nucleus - and contains majority of an atom's mass and all it's positive charge carried by protons
  • Evidence of Isotopes

    Mass spectrometry was used for the first time by J.J Thomson. He discovered that neon was composed of two different kinds of atoms and this proved the existence of isotopes in a stable element.
  • Atomic Structure

    Bohr worked for J.J Thompson in England when he was introduced to Rutherford and under his guidance he began studying the properties of atoms. Using Rutherford's description of the nucleus and other theories Bohr developed a picture of atomic structure and what occurs inside an atom
  • Henry Moseley's Theory

    Moseley discovered that the basic difference between elements is the number of protons they have. By arranging the elements in order of atomic number increasing rather than their atomic weight the flaws in Mendeleev's table disappeared. He saw gaps in this new periodic tables and predicted the existence of four new elements
  • Bohr Model

    Based on quantam mechanics and modified the Rutherford Model. Presented an atom as a small, positively charged nucleus surrounded by orbiting electrons. Also states that the electron's orbit of smallest radius corresponds to its lowest energy level (ground state). This model solved the problem of the unstable electron orbits and enabled to calculate and predict the wavelengths of light present in the line spectra of hydrogen
  • Death of Henry Moseley

    Died in battle during WWII Gallipoli, Turkey.
    Following his death the British Government put a ban on scientists serving on the front lines
  • Transmutation of an Element

    Ernest Rutherford became the first person to deliberately transmute one element into another using nitrogen atoms with alpha particles to create oxygen
  • Discovery of Neutrons

    The neutron was discovered by James Chadwick under the direction of Ernest Rutherford. He identified neutrons as a product of the alpha particle bombardment of Beryllium. Chadwick's discovery was pivotal towards nuclear fission and led towards the development of the atomic bomb
  • Protons and the Nucleus

    Ernest Rutherford coined the term 'proton' and theorised the existence of the nucleus alongside colleague and former student James Chadwick
  • Death of Ernest Rutherford

    Cambridge, United Kingdom
    Rutherford had a large influence upon this field and mentored prominent scienctists in the discovery and development of the periodic table including James Chadwick and Neils Bohr
  • Death of J.J. Thomson

    Cambridge, United Kingdom
  • Death of Neil Bohr

    Copenhagen, Denmark
  • Death of James Chadwick

    Cambridge, United Kingdom