## Atomic Mass Unit

The individual masses involved involved in nuclear reactions are tiny. The mass of a proton is
$1.672621 \times 10^{-27} kg$
, almost the same as the mas of a neutron. This is not a convenient mass unit. We define a convenient mass unit as one twelfth the mass of a Caron- 12 atom, called the atomic mass unit, labelled
$u$
.
$1 u=\frac{1}{12} (mass \: of \: {}^{12}_6C)=1.660539 \times 10^{-27} kg$

In terms of the atomic mass unit the mass of a proton is
$1.007276$

The mass of a neutron is
$1.008665 u$

The mass of an electron is
$0.000549 u$