The atomic nucleus: Inside the atom

日期:2017-08-13 03:00:24 作者:空检匝 阅读:

By Phil Walker Read more: “Instant Expert: The atomic nucleus“ The idea of atoms as the ultimate, indivisible particles of matter dates back to the pre-Socratic philosophers of Ancient Greece. It worked amazingly well for many hundreds of years, and was the bedrock on which our burgeoning understanding of the elements – the new science of chemistry – was built from the 18th century onwards. All that changed 100 years ago this year, with the first glimpse of something nestling at the heart of the atom, something vastly smaller than it, yet containing almost all its mass: the atomic nucleus. The impact of this discovery was so profound that the past century has sometimes been called “the nuclear age”. Well into the 21st century, however, the interior workings of the nucleus are still far from perfectly understood In 1897, the British physicist J. J. Thomson was investigating streams of particles given off by metal electrodes placed under high voltage in a vacuum. These particles turned out to be much smaller than atoms and, unlike neutral atoms, negatively charged. The discovery of these “electrons” put paid to the idea that the atom was uniform and indivisible. To maintain the atom’s overall electrical neutrality, Thomson suggested that electrons were embedded inside it like plums in a “pudding” of positive charge. By 1908, New Zealander Ernest Rutherford, working with his assistant Hans Geiger at the University of Manchester, UK, had revealed a different picture. When fired from a radioactive source,