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An unstable nucleus becomes more stable by emitting
an alpha particle, beta particle or gamma radiation.
It consists of two protons and two neutrons.
When it is released by an unstable nucleus, the
atom's mass no. goes down by 4 and it's atomic
no. by 2.
A particle is an electron created and emitted
by a nucleus that has too many neutrons.
A neutron changes into a proton and a particle,
which is instantly emitted at high speeds by the
When a is released the atomic number goes up
by 1 but the mass stays the same.
It is emitted by some unstable nucleus after
alpha or beta particles have been emitted. It has
no mass or charge and doesn't change the mass or atomic
The Discovery of the nucleus:
Ernest Rutherford used alpha particles to find out more
about the structure of an atom.
He fired alpha particles at a thin metal foil and measured
the number of particles deflected per second through
different angles. The results showed that...
Most particles went straight through the
The number of particles deflected per min
decreased as the angle of deflection
About 1 in 10000 particle were deflected by
more than 90º.
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From the results Rutherford deduced that there was a
nucleus, which is...
Positively charged as it repels alpha
Much smaller than the atom because most
particles passed through without deflection
Where most of the mass of the atom was
He used his theory to estimate the diameter of the nucleus
and found it was about 100000 times smaller than the atom.
Rutherford's nuclear model was quickly accepted because...…read more
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Two small nuclei release energy when they fuse together to form a
nucleus. This only happens if the mass of the product nucleus is
no more than 55.
Fusion is how the sun and other stars make energy. The Sun is
made up from around 75% hydrogen and 25% helium. The core is
so hot that it consists of a `plasma' of bare nuclei with no
electrons. It is these that fuse together.
When two protons fuse, they make a `heavy hydrogen' H-2.…read more