Answer: 9.1093837015 × 10−31 kg, which is only 1/1,836the mass of a proton.
Step-by-step explanation:
The rest mass of the electron is 9.1093837015 × 10−31 kg, which is only 1/1,836the mass of a proton. An electron is therefore considered nearly massless in comparison with a proton or a neutron, and the electron mass is not included in calculating the mass number of an atom.