JOSEPH JOHN THOMSON
Joseph John Thomson
was born in 1856 at Cheetham Hill - near Manchester. He studied
sciences in Manchester. After studies he moved to Cambridge, were
he became Rayleigh's assistant.
After Rayleigh had left, at the
age of 28 Thomson became the head of the experimental physics
faculty and of the Cavendish Laboratory. He was also a lecturer at
the universities in Princeton and New Haven (the Yale University)
in the United States.
His major achievement
was the determination of the ratio of charge to mass of the
molecules composing cathode
radiation, and the conclusion that those rays consisted of
identical molecules, which were called electrons
(he presented this hypothesis on 30th April 1897). Thomson
perceived an atom as a charged sphere with electrons inside
(the "plum cake"
model). That model was good enough to explain many physical and
chemical phenomena - electrolysis, electron emission.
The scientist also
discovered that in the substances he researched the number of
electrons in an atom equalled half of the mass number. He
investigated and analysed beams of positive ions emerging at the
cathode inside the tube, similar to the one due to which he
discovered electrons. In 1913 together with Francis Aston he discovered the existence
of permanent neon isotopes.
In 1906 Joseph John
Thomson received a Nobel prize.
In 1915 he became the
chairman of the Royal Society. He remained in the position until
1920 when he withdrew from scientific activity. Thomson died on
30th August 1940.