William crookes atomic theory
The son of a wealthy tailor, he inherited a considerable fortune from his father and at the age of 24 he decided to set up a private laboratory and establish himself as an independent advisor, consultant and scientific researcher. William Crookes (J– April 4, 1919) always opted for going it alone. From discovering an element to investigate mediums Much less well known, however, is his ambiguous relationship with the world of spiritualism and the paranormal, a dark period in his life to which he devoted four years, and which almost ended his scientific career and ruined his reputation. He also founded and edited scientific journals and became president of the Royal Society, the oldest scientific society in the world. But he was also the inventor of modern sunglasses (with a 100% ultraviolet filter) and ingenious devices to see the disintegration of radioactive atoms or to detect the intensity of electromagnetic radiation. He left his mark above all with his invention of the cathode ray tube and the discovery of a chemical element, thallium. Today a number of smaller particles are found to constitute atoms. These particles constituting the atom are called subatomic particles.William Crookes is recognised today as one of the great scientists of the Victorian era. This conclusion raised a question, "If the atom was divisible, then what were its constituents?". In other words, Dalton’s theory of atomic structure failed partially. This meant that the atom is not indivisible as was believed by Dalton and others. This led Thomson to conclude that all atoms must contain electrons. Since it was observed that the nature of cathode rays was the same irrespective of the metal used for the cathode or the gas filled in the cathode ray tube. These particles constituting the cathode rays were later called electrons. In all the cases the charge to mass ratio (e/m) was found to be the same The nature of cathode rays generated was independent of the nature of the gas filled in the cathode ray tube as well as the nature of metal used for making cathode and anode. The particles constituting cathode rays have negligible mass but travel very fastĬathode ray particles carry negative charge and are attracted towards positively charged plate when an external electric field is applied The particles constituting cathode rays carry mass and possess kinetic energy This conclusion was drawn from the experimental observations when the experiment was done in the presence of an external electric field.įollowing are the important properties of cathode rays: Thomson showed that the rays were made up of a stream of negatively charged particles. In the absence of external magnetic or electric field these rays travel in straight line. These particles were shown to travel from cathode to anode and were called cathode rays. It was observed that when very high voltage was passed across the electrodes in evacuated tube, the cathode produced a stream of particles. The negatively charged electrode is called cathode whereas the positively charged electrode is called anode. These electrodes are connected to a high voltage source. An evacuated tube is the one from which most of the air has been removed. A cathode ray tube consists of two metal electrodes in a partially evacuated glass tube. In 1885, Sir William Crookes carried out a series of experiments to study the behaviour of metals heated in a vacuum using cathode ray tubes.
These particles were called electrons, protons and neutrons. The electrons are negatively charged whereas the protons are positively charged. It was shown to be made up of even smaller particles. However, towards the end of nineteenth century, certain experiments showed that an atom is neither the smallest nor indivisible particle of matter as stated by Dalton. The Dalton's theory could explain the law of conservation of mass, law of constant composition and law of multiple proportions known at that time. Dalton's atomic theory, proposed in the year 1803, considered the atom to be the smallest indivisible constituent of all matter.