Ernest Rutherford (1871-1937) was a New Zealand physicist who’s often referred to as the father of nuclear physics. So basically, he’s a pretty big deal.
Over the course of his career, Rutherford aided the world’s understanding of nuclear physics in a way that hasn’t been seen since – but his most memorable contribution is most likely his aptly named Rutherford experiment of 1909, where alpha particles were fired at thin gold foil to demonstrate that most of the mass was concentrated in the centre of the atom.
The experiment was in fact carried out by Geiger and Marsden, but it was Rutherford who consequently explained why the vast majority of alpha particles were only slightly deflected from their paths. This led to the Rutherford model of the atom, with a dense, positively charged nucleus at the centre and negatively charged electrons orbiting it.
Although Ernest Rutherford was from New Zealand, some of his most famous work was done in the UK, at the Victoria University in Manchester (now the University Of Manchester). Having said that, he received his Nobel Prize in Chemistry for discovering the concept of radioactive half-life, which he discovered whilst at the McGill University in Canada.
But back to Rutherford’s experiment! Since most of the particles passed straight through the foil, or were only slightly deflected, this meant that atoms were mostly empty space, not like a plum pudding as J.J. Thomson previously thought (though he didn’t call it a plum pudding).
This meant that there must be a central nucleus where all the positively charged particles were concentrated, which was the reason for the deflections, then a lot of empty space, before the cloud of negatively charged electrons orbiting the nucleus.
In Rutherford’s experiment, when an alpha particle hit the zinc sulphide screen, the screen would emit light. This is because the zinc sulphide screen, or scintillator, acted as a detector for alpha particles that had passed through the piece of gold foil. Once they struck the screen, light would be emitted, indicating that an alpha particle had been detected. And there you have it!