# When the mass of the boron atom is calculated, the mass of the electrons is ignored. Why is the mass of the electrons ignored?

The mass of a proton is approx. 1.673×10^(−27)* kg; the mass of a neutron is slightly larger. On the other hand, the rest mass of an electron is approx. $9.119 \times {10}^{-} 31 \cdot k g$, approx. 4 orders of magnitude difference. Should electron mass be ignored, we are not going to sacrifice too much accuracy.