The protons and electrons were discovered in 1886 and their properties were completely determined till 1895. Rutherford predicted in 1920 that some kind of neutral particles having mass equal to proton must be present in an atom. Chadwick discovered neutron in 1932 and was awarded Nobel Prize in Physics in 1935. EXPERIMENT A stream of…
As the atom was considered neutral, therefore, soon after the discovery of negatively charged particles i.e., electrons, scientists tried to discover a positively charged constituent of atom. In 1886, Eugene Goldstein used a discharge tube with perforated cathode. He observed a glow in the region behind the cathode. This glow was consequence of rays, which…
To study the properties of cathode rays systematic investigations were made by W. Crooks, J.J. Thomson and J. Perrin. They established the following properties of cathode rays: Cathode rays are negatively charged. In 1895, J.Perrin showed that cathode rays are deflected in a magnetic field perpendicular to the line joining the two poles. In 1897,…
Discharge tube The discharge tube is a glass tube having two electrodes sealed into it connected to a vacuum pump to reduce the pressure of the gas taken into it. A slit is placed in the tube to get a sharp beam of radiations. Experiment: William Crooks a British scientist studied the passage of electricity…
“The solids having metallic bonds in them are called metallic solids.” Electron Gas Theory: The first theory of metallic bonding is called electron pool or electron gas theory. This theory was proposed by Drude and extended by Loren (1932). According to this theory, each atom in a metal crystal loses all of its valence electrons….
“The crystals consisting of molecules, which are held together through Vander Waals’ forces, are called molecular crystals.” Explanation: Since Van der Waals’ attractive forces are weaker, therefore, molecular crystals are soft and have low melting points and low lattice energies. These crystals are poor conductors of electricity. This is because electrons are bound to individual…