Question

all the mass of an atomic is concerned in the nucleus.

Answer 1

Atomic nucleus is packed with protons and neutrons; each with mass of 1 amu. Electrons hover around the nucleus in several energy levels; each with negligible mass. The total mass mass of electrons in an atom itself is negligible in comparison to even either one proton or neutron.

Answer 2

the atomic nucleus is the small ,dense region consisting of protons and neutrons at the center of the atom discover in 1911 by Ernest Rutherford