What is nucleus

Nucleus:-

         The nucleus lies in the center of an atom. It has particles in it called (protons and neutrons). Around the nucleus there are electrons revolving in the circular paths called orbits or shells.

            The size (which is infact diameter) of the nucleus is between 1.6 fm (10⁻¹⁵ m) (for a proton in light hydrogen) to about 15 fm. Although it is only a very small part of the atom, the nucleus has most of the mass. Almost all of the mass in an atom is made up from the protons and neutrons in the nucleus with a very small contribution from the orbiting electrons.