Atomic firsts

    Ernest Rutherford is one of the most famous scientists to have worked in Britain. His most celebrated achievement was to ‘split the atom’, a concept which caught the imagination of the public at the time of its development, and continues to do so today.

    Born in New Zealand, Rutherford came to England on a scholarship from the Commission of the 1851 Great Exhibition. In 1895 he began work at the Cavendish Laboratory at Cambridge University, under the guidance of J.J. Thomson.

    Rutherford’s first area of research was into radio waves, discovered a few years before by Hertz. However with the encouragement of Thomson, Rutherford turned his attentions to the newly discovered X-rays. It was during this period that J.J. discovered the electron through his experiments on cathode rays in 1897. How these electrons fitted into the atom was still unclear. Thomson himself thought that they were embedded in a sphere of positive charge, known as the ‘plum-pudding’ model.

    However in 1913 Rutherford, along with the Danish physicist Niels Bohr, dispelled J.J.’s theory and proved that an atom was made up of a positively charged nucleus with electrons orbiting around it.

    Initially Rutherford discovered the existence of a nucleus by considering the work of Hans Geiger and Ernest Marsden, two colleagues at Manchester University. They had bombarded gold foil with alpha particles. The results were surprising. Rather than the particles being deflected, most went through the foil, and a small number bounced back towards the source.

    In 1911, Rutherford explained why this happened. He proposed that the atom contained a nucleus in which most of the atom’s mass and positive charge must be centred. This theory was then expanded by Bohr who believed that the electrons, the negatively charged particles within the atom, rotated in specific orbits around the nucleus. For example, a neutral hydrogen atom is the simplest form of atom. It has a nucleus with a single positive charge and one electron circling it. The model looks like a mini solar system.

    So as Rutherford expanded these ideas at Manchester University, he completed his most famous experiment – splitting the atom. He was the first to cause an artificial break-up of an atomic nucleus as well as changing one element into another. This he achieved by firing alpha-particles into an atom. Occasionally one caused part of the nucleus to break off.

    Rutherford then proposed that a positive charge in the nucleus was made up of units, the basic unit being the nucleus of the hydrogen atom. He suggested the term 'proton' for this unit.

    Albert Einstein had already developed the idea of matter converting into energy. Rutherford’s theory provided proof for this idea.

    Though these discoveries were fundamental to the advancement of nuclear physics, Rutherford was awarded with a Nobel Prize for Chemistry! This amused him greatly as his work had been in atomic physics.

    Advances in the understanding of the atom and its structure have given rise to developments and theories in several areas of science. These include one of the fundamental questions: how did the universe begin? One answer is the Big Bang theory, which proposes that the universe emerged from nothing. Immediately after the bang the new universe began expanding, filling up with subatomic particles, including electrons.

    Related Links