Question

How an atom is neutral, in case of mass , i.e. How the total mass of electron is equal to the nucleus.....

Answer 1

As, mass of nucleus = mass of proton + mass of neutron
But , mass of proton = mass of electron
So, the question come in our mind that if mass of nucleus = mass of electron then whare the mass of proton and mass of neutron gone
So when the nucleus is made by combination of proton + neutron then some of energy in the form of mass release from the nucleus.. As , u know same charge can't combine it requires lot of energy
So , this energy relesed make mass of nucleus equal to mass of electrons in a atom...