Question

sodium atom and sodium Ion have the same mass why​

Answer 1

sodium atom and sodium ions have same mass although the difference in electron

it is so because the mass of an atom is the sum of mass of proton and neutron and not the electron because electron has negligible mass

hence the difference in the electron did not change the value of mass of same atom

that is why mass of sodium atom and sodium ion is same

Answer 2

Because the mass of an atom depends on the total mass of protons and neutrons.

The no. of protons and neutrons of a sodium atom and a sodium ion is equal. So, their masses are equal. Although, a sodium atom has 11 electrons and a sodium ion has 10 electrons as the mass of electron is considered negligible.