Question

Is the mass of an electron 1 amu?

Answer 1

Answer:

The mass of an electron is listed as being equal to

m_electron = 9.10938356 ⋅10^(−31) kg

The unified atomic mass unit or u is defined as the mass of one nucleon, that is a proton or a neutron. More specifically, one unified atomic mass unit is equal to 1/12th

of the mass of a carbon-12 atom.

A carbon-12 atom has six protons and six neutrons in its nucleus and a molar mass of

12.0 g/mol. This means that you can find the value of u in kilograms by using Avogadro's number 12.0 g/mol⋅

1

mole

6.022⋅10^(23) atoms = 1.992693457 ⋅10^(−23) g/atom

Since you need

1/12th of the mass of a single carbon-12 atom, it follows that you have

1 u = 1.660538922⋅10^(−27)kg

This means that the mass of an electron expressed in unified atomic mass units will be equal to

9.10938356⋅10(−31) kg⋅1 u/(1.660538922⋅10^(−27)kg

= 5.4858.10^(−4)u = 0.0005485 u