Structure of the Atom

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Structure of Atom

When scientists started exploring matter, they discovered that the smallest particle of an element that maintains its chemical identity through all chemical and physical changes is called and 'atom'. Just how small these atoms are can be made out if you realize that there are about 60,000,000,000,000,000,000 atoms in a pinhead! Everything that exists in our universe is made up of this tiny particle called atom. The computer you are working on is made up of atoms. All the people you know and all the modern structures of the cities are made up of atoms. In fact everything, the water, the earth, the air, and even outer space is made up of atoms. Let us right away meet those who scripted a 'mighty story' of a 'miniscule' atom.

• John Dalton (1766 - 1844)

Born in the poor family of a weaver in England, John Dalton rose to become a teacher and later the Principal of a school. In 1793, he left for Manchester to teach physics and chemistry in a college.

In 1801, he observed and discovered the law of expansion of gases on heating. He also enunciated the law of partial pressures and found methods of determining vapour pressure of gases. He invented the dew point hygrometer.

In 1803, he gave the famous atomic theory. He calculated, the atomic weight of many elements, invented chemical symbols, established the Law of multiple proportions and gave the correct formula for ether.He explained the nature of aurora borealis and suggested that the atmosphere contained a magnetic constituent. His contribution towards enrichment of science has been varied.

• J.J Thomson (1856 - 1940)

J.J Thomson is usually credited with the first 'modern' model of the atom, the so-called 'raisin pudding' model. In it, he pictured a sphere of positive charges mixed together with an equal number of electrons. For his theoretical and experimental investigations into the electron and the conduction of electricity by gases he was awarded the 1906 Noble prize in Physics. He and his student Rutherford were the first to demonstrate the ionization of air by X-rays.

• Ernest Rutherford (1871 - 1937)

Born in New Zealand, Ernest Rutherford was one among the twelve children of a farmer. His parents gave him university education with great difficulty. A brilliant student - he worked with J.J Thomson at Cambridge University to study the effect of electricity through air. He studied the spontaneous disintegration of radium.

He is well known for the scattering experiment of alpha rays through matter, which led to the famous structure of atom in 1911. He was awarded the Nobel Prize in 1908.

The famous words of Rutherford on completing the alpha rays scattering experiment were: 'It was quite the most incredible event that has ever happened to me in life. It was almost as if you fired a 15 inch shell into a piece of tissue paper and it came back and hit you'.

• James Chadwick (1891 - 1976)

James Chadwick, born at Cheshire, England, grew up to be a famous chemist. One of the most brilliant students of Rutherford, he built the first cyclotron of U.K. In 1932, he made the fundamental discovery of neutron, proving that it was the most powerful particle for initiating nuclear reactions. By energy calculations he was able to calculate the mass of the neutron. He was awarded the Nobel Prize in Physics in 1935, for the discovery of neutron.

• Neils Bohr (1885 - 1962)

Neils Bohr was a eminent Danish Physicist who obtained his doctorate in theoretical Physics in 1911. He made a great contribution towards the understanding of atomic structure and quantum mechanics. He was awarded the Nobel Prize in Physics at the young age of 37, in 1922, primarily for his work on atoms. During the World War II, he went to USA and was one of the witnesses of the atomic explosion in New Mexico in 1945. Later he returned to Copenhagen and promoted the peaceful use of atomic energy. In 1957, he was awarded the prize for 'Atom for Peace'. Structure