discovery of the atomic atom

Electron - Discharge Tube experiments These experiments were conducted in detail by J.J. Thomson and he studied the passage of electricity through gases at extremely low pressure in a cylindrical glass tube. It was discovered that at extremely low pressure, gases become conductors of e..

Atom was derived from the Greek word 'atoms', meaning 'indivisible'. Thus, it was considered to be indivisible.Atoms of the same element are identical in shape, size, mass and other properties.Atoms cannot be created, divided or destroyed during any che..

Atomicity is the number of atoms of an element present in one molecule of that element. They can be monoatomic (He), diatomic (H 2 ), triatomic (O 3 ) and polyatomic (S 8 ..

Hydrogen is diatomic (H 2 ) whereas alkali metals are monoatomi..

Summary Atom is the smallest particle of an element, which maintains its identity throughout chemical and physical changes. Atoms are made up of three fundamental particles: electrons, protons and neutrons. Discharge tube experiments by William Crookes and J.J. Thomso..

. 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..

Since the atom is electrically neutral there must be positively charged particles present in the atom to neutralize the negative charges of the electrons. Goldstein experimentally proved the existence of protons in the atom..

Discovery of Radioactivity - The discovery of the phenomenon of radioactivity was purely accidental. In 1896, Henry Becquerel, a French scientist accidentally found that in presence of salt of uranium, photographic plates got heavily fogged even though they were wrapped in opaqu..

In view of new discoveries about atoms, Dalton's atomic theory was modified as given below: * Atom is no longer indivisible as it has a complex structure of sub atomic particles (electrons, protons and neutrons). * Atoms of..

Production of cathode rays - In 1885, Sir William Crookes carried out a series of investigations into the behaviour of metals heated in a vacuum. The experiment of Crookes and others showed that a heated cathode produced a stream of radiation, which could cause gases at low pressure to glow and whi..