The entire mass of an atom resides in its nucleus.
According to Rutherford's atomic model, the size of the nucleus is very small as compared to the size of the atom.
What did Rutherford conclude regarding the atomic mass? (i) Mass of the atom is uniformly distributed. (ii) Nucleus of an atom is much heavier than electron. (iii) Nearly all the mass of an atom resides at the centre of an atom. (iv) Nucleus of an atom is lighter than the electron.