Ernest Rutherford is regarded as the father of nuclear science. He was born in New Zealand in 1871 and went on to study, train, and teach in the United Kingdom and Canada.
Nuclear physics history: In 1908, Rutherford, at the age of 37, was awarded the Nobel Prize in Chemistry for his investigations into the disintegration of the elements and the chemistry of radioactive substances.
Rutherford is famous for discovering the structure of an atom. He is also credited with the discovery of detection of magnetic waves which later led to the invention of the radio.
He also has a unit named after him. “Rutherford” is used in radioactivity and measures million breakdowns per second.
Rutherford is known for the “scattering experiment” that led to the discovery of the properties of atoms.
Rutherford observed that the radiation emitted by radioactive elements came in two forms, he named them alpha and beta.
Alpha particles are positively charged and wouldn’t penetrate a piece of paper.
Beta particles are negatively charged and would pass through several pieces of paper.
In the scattering experiment, a beam of alpha particles (He2+ ions) were directed at a thin gold foil.
Rutherford had expected the alpha particles to travel through the gold foil, and maybe change direction a little bit.
Instead, Rutherford and his team discovered that :
- Most of the α-particles passed straight through the foil
- Some of the α-particles changed direction but continued through the foil
- A few of the α-particles bounced back off the gold foil.
- Some are deflected through small angles
From the results of the scattering experiment, Rutherford began to piece together a picture of the atom.
He concluded that since the gold foil was two thousand atoms thick, and the majority of the α-particles passed through deflected, it would seem that the atoms were mostly empty space.
The alpha particles that were undeflected through large angles, sometimes greater than ninety degrees, seemed to indicate that within the gold atom there were very massive positively charged regions capable of turning back the alpha particles – much like a tennis ball bouncing off a wall.
- This happens because the positive α-particles are repelled by the positive nucleus which contains most of its mass
- A very small number are deflected straight back. This is because the nucleus is extremely small.
In 1911, Rutherford announced his model of that atom. In his theory, the atom contains a very tiny nucleus at its center, which is positively charged and contains the protons and virtually all the mass of the atom since the proton is much more massive than the electron.
Surrounding the nucleus are the much lighter electrons that have an equal number of negative charges.
This model of the atom was much closer to the modern view of the atom and replaced the concept of the featureless, indivisible spheres proposed by the ancient Greek philosopher Democritus, which had been over two millennia.
A new era of history of nuclear science had begun with Rutherford who continued to work on radioactive material and died in 1937