grp. 5 II-2 JJ Thomson

Biography

      Sir Joseph John “J. J.” Thomson, OM, FRS (18 December 1856 – 30 August 1940) was a British physicist and Nobel laureate. He is credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer. Thomson was awarded the 1906 Nobel Prize in Physics for the discovery of the electron and for his work on the conduction of electricity in gases.
     Joseph John Thomson was born in 1856 in Cheetham Hill, Manchester, England. His mother, Emma Swindells, came from a local textile family. His father, Joseph James Thomson, ran an antiquarian bookshop founded by a great-grandfather from Scotland (hence the Scottish spelling of his surname). He had a brother two years younger than him, Frederick Vernon Thomson.
    His early education was in small private schools, and demonstrated great talent and interest in science. In 1870 he was admitted to Owens College. Being only 14 years old at the time, he was unusually young. His parents planned to enroll him as an apprentice engineer to Sharp-Stewart & Co., a locomotive manufacturer, but these plans were cut short when his father died in 1873.[1] He moved on to Trinity College, Cambridge in 1876. In 1880, he obtained his BA in mathematics (Second Wrangler and 2nd Smith's prize) and MA (with Adams Prize) in 1883.[2] In 1884 he became Cavendish Professor of Physics. One of his students was Ernest Rutherford, who would later succeed him in the post. In 1890 he married Rose Elisabeth Paget, daughter of Sir George Edward Paget, KCB, a physician and then Regius Professor of Physic at Cambridge. He fathered one son, George Paget Thomson, and one daughter, Joan Paget Thomson, with her. One of Thomson's greatest contributions to modern science was in his role as a highly gifted teacher, as seven of his research assistants and his aforementioned son won Nobel Prizes in physics. His son won the Nobel Prize in 1937 for proving the wavelike properties of electrons.
      He was awarded a Nobel Prize in 1906, "in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases." He was knighted in 1908 and appointed to the Order of Merit in 1912. In 1914 he gave the Romanes Lecture in Oxford on "The atomic theory". In 1918 he became Master of Trinity College, Cambridge, where he remained until his death. He died on August 30 1940 and was buried in Westminster Abbey, close to Sir Isaac Newton.

     Thomson was elected a Fellow of the Royal Society on 12 June 1884 and was subsequently President of the Royal Society from 1915 to 1920.

J.J Thomson's Atomic Model

        Plum Pudding Model:
        Thomson proposed that the atom had these negatively charged particles (electrons) that floated in a cloud of positive charge. So the electrons were like plums baked in a bowl of pudding. The positive charges (protons) filled the whole atom (pudding).
       
Atomic Structure

Atoms are composed of 3 main subatomic particles: Electrons, Protons and Neutrons. There are even smaller subatomic particles, such as quarks and gluons, but for the purposes of understanding the basic composition of matter, these 3 are sufficient.
The Nucleus
At the very center of an atom is the nucleus.
It is a small, dense, positively charged “core” that contains most of the atom’s mass, and is composed of the atom’s protons and neutrons.

Protons
Protons are tiny, positively charged particles found in the nucleus.
Their mass is only about 1.7 x 10-24g, or 1 atomic mass unit (amu).
Protons are incredibly important to the identity of an atom/element - each elemental atom has a unique number of protons in its nucleus. Boron, for example has 5 protons, while Carbon has 6. Variations on atoms (which we will discuss later as isotopes and ions) always have the same number of protons.
The number of protons an atom has is called its atomic number.

Neutrons
Housed next to the protons are particles called neutrons.
These particles have no charge, and are considered to have about the same mass as a proton. In a general, model atom, neutrons exist in the same number as protons. That is, in a model atom with 5 protons, there will be 5 neutrons. 6 protons, 6 neutrons, and so on.