# In atomic mass units, what is the mass of an electron?

##### 1 Answer

#### Explanation:

The mass of an electron is listed as being equal to

#m_"electron" = 9.10938356 * 10^(-31)"kg"#

The *unified atomic mass unit*, or **nucleon**, that is a proton or a neutron. More specifically, one unified atomic mass unit is equal to

A carbon-12 atom has **six protons** and **six neutrons** in its nucleus and a molar mass of *kilograms* by using **Avogadro's number**

#12.0"g"/color(red)(cancel(color(black)("mol"))) * (1color(red)(cancel(color(black)("mole"))))/(6.022 * 10^(23)"atoms") = 1.992693457 * 10^(-23)"g/atom"#

Since you need

#1/12 * 1.992693457 * 10^(-23)color(red)(cancel(color(black)("g"))) * "1 kg"/(10^3color(red)(cancel(color(black)("g")))) ~~ 1.660538922 * 10^(-27)"kg"#

Therefore, 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)color(red)(cancel(color(black)("kg"))) * "1 u"/(1.660538922 * 10^(-27)color(red)(cancel(color(black)("kg")))) = 5.4858 * 10^(-4)"u"#