Most of the mass of the atom is provided by what?
The nucleus of the atom accounts for about
We know that the proton and neutron have very similar masses (though not identical!) and that each outweighs the electron by nearly a 2000:1 ratio.
So, the nucleus is the location of virtual all the mass of the atom.
This is why, for example, if we need to look up the molar mass of a sodium ion,