Rutherford
RutherfordErnest Rutherford was born in Nelson, New Zealand.
Rutherford demonstrated his abilities as a scientist early
on while working on his B.Sc. at the University of New
Zealand in 1894. He showed that the magnetization can
be removed from a magnetized iron needle by dissolving
the surface layer of the metal in acid.
He began work at Cambridge in 1895 and was a
professor at the University of Manchester from 1907 on.
It is during this time period that Rutherford made his
most important discoveries. Most of Rutherford's work
was centered on radioactivity. He is the one who named
the alpha and beta particles. In 1911, Rutherford
conducted his famous "gold foil" experiment. He directed
alpha particles at a thin sheet of gold foil and expected
the particles to simply travel straight through the foil.
However, he obtained very different results. Although
many of the particles did in fact go straight through the
foil, some of them were deflected at large angles.
Rutherford concluded that the deflections of the alpha
particles were caused by a center of positive charge that
contained most of the atom's mass (the nucleus). He also
explained that the particles that went straight through the
foil did so because the atom is mostly empty space and
that the distance between electrons and the nucleus is
vast compared to the size of the nucleus itself.
In 1919, he discovered the "artificial disintegration" of
nitrogen. His experiments show that under alpha
radiation, nitrogen is decomposed and hydrogen is
formed. Rutherford also devised an electrical method for
counting the number of alpha particles emitted from
radioactive substances. Using this method, he measured
the number of alpha particles expelled per second from
one gram of radium to be 34000.
Before Rutherford, the smallest particle of matter was
represented as a solid ball. Rutherford's experiments with
the decay of radioactive elements caused him to think in
terms of a more definite structure. He observed that the
disintegration of elements was accompanied by emissions
of positive helium and of negative particles of almost no
mass. He then concluded that an atom is not the last unit
of matter, rather, it is composed of subatomic particles.