(4) less than the mass of a neutron

(3) greater than the mass of a proton

(2) equal to the mass of a neutron

(1) equal to the mass of a proton

4 Compared the energy of an electron in the second shell of an atom of sulfur, the energy of an electron in the (1) first shell is lower (2) first shell is the same (3) third shell is lower (4) third shell is the same