Alpha Particle Scattering

Alpha Particle Scattering

In 1909, Ernest Rutherford and his student Ernest Marsden conducted the alpha particle scattering experiments

They fired positively charged alpha particles at an extremely thin sheet of gold

From the plum pudding model, they were expecting the particles to pass straight through or be slightly deflected at most

This was because the positive charge of each atom was thought to be very spread out through the 'pudding' part of the atom

But whilst most of the particles did go straight through, some were deflected more than expected, and a small number were deflected backwards

Rutherford came up with an idea to explain this new evidence - the nuclear model of the atom

In this, there's a tiny, positively charged nucleus at the centre, where most of the mass is concentrated

A 'cloud' of negative electrons surrounds this nucleus - so most of the atom is empty space

When alpha particles came near the concentrated, positive charge of the nucleus, they were deflected

If they were fired directly at the nucleus, they were deflected backwards, otherwise they passed through the empty space