jun 1, 1910 - Discovery of Nucleus:
The nucleus was discovered in
1910 by Leiger and Marsden.
In their experiment they fired positively
charged particles (alpha particles)
at the thinnest piece of gold they could make.
They expected the particles to
pass through the cloud of
positive charges as proposed by Thomson.
This didn't happen. Some
of the particles were repelled backwards.
This proved the plum-pudding
model wrong. Rutherford therefore
suggested in 1911 that the
positive charges are concentrated
at the atom