Modern Atomic Theory

Modern Atomic Theory Access and download the application ‘atom.phys’ in your mobile by using the provided URL or QR code. Click ‘ Modeling ’ to build the structure of an element by making changes in electron, proton and neutron. Click ‘ Nuclear decays ’ to know how new elements are formed because of the decay/ destruction of atoms. Finally click ‘ Tests ’ to check your knowledge by answering the questions. Steps To enable the students to build structure of different elements with electrons, protons and neutrons. They also know how new elements are formed as a result of Nuclear decays. INTRODUCTION You have learnt, in your lower classes that matter is around us everywhere. Matter is made of atoms. Curiously the idea of atom was first proposed by the Greek philosophers in the fifth century BC (BCE). But, their theory was more philosophical than scientific. The first scientific theory of the atom was proposed by John Dalton. Few of the postulates of Dalton’s theory about an atom were found incorrect by the later on studies made by J.J. Thomson, Rutherford, Neils Bohr and Schrodinger. In the light of the result of the researches most of the limitations of the Dalton’s theory were removed and a new theory known as the modern atomic theory was put forward. ‘The main postulates of modern atomic theory’ are as follows: ‹ An atom is no longer indivisible (after the discovery of the electron, proton, and neutron). ‹ Atoms of the same element may have different atomic mass. (discovery of isotopes Cl , Cl ). ‹ Atoms of different elements may have same atomic masses (discovery of Isobars Ar , Ca ). ‹ Atoms of one element can be transmuted into atoms of other elements. In other words, atom is no longer indestructible (discovery of artificial transmutation ).