Q. What do you mean by nucleus of the atom?
The nucleus of an atom for the reason that atoms have no net electrical charge scientists reasoned that if an atom contains particles of negative charge it must as well contain particles of positive charge. In 1911 Ernest Rutherford perform experiments in which he aimed a ray of alpha particles (positively charged helium nuclei) at a thin sheet of gold. The fact that some of these heavy particles were deflected almost directly backwards revealed that the positive charge of an atom along with nearly the entire atom's mass is concentrated in a very small region in the centre of the atom. This optimistically charged mass is called the nucleus of the atom. The particles that comprise the positive charge of the nucleus are called protons and each has a charge of 1(equal to but opposite the charge of an electron).