Home Preparation for National Talent Search Examination (NTSE)/ Olympiad
Chapter : 4. Structure Of Atoms
Rutherford model of an atom
(B) Rutherford model of an atom Rutherford and his co-workers made a fundamental contribution in understanding the structure of the atom and establishing the presence of a small nucleus in the atom. They performed a number of experiments known as scattering experiments. They took very thin sheets of gold foil (only 4 × 10–5 cm thick) and bombarded it with a stream of alpha (α) particles. The alpha particles are positively charged helium ions (He2+) which carry two units of positive charge and mass four times that of an atom of hydrogen (i.e., mass of helium ions = 4 a.m.u.). These are emitted from radioactive elements such as radium. Following important observations : Most of the fast moving α-particles passed straight through the gold foil without any deflection from their original path. Some of the α-particles were deflected from their path through small angles. Very few (about 1 in 12,000) did not pass through the foil at all but suffered large deflections (more than 90º) or even came back in the direction from which they came.