Write about atomic mass.

(N/A) The atomic mass of an atom is extremely small because atoms are very tiny.
Today,sophisticated techniques like mass spectrometry are used to determine atomic masses accurately.
Initially,hydrogen was assigned a mass of $1$ (without units) as it is the lightest atom,and other elements were assigned masses relative to it.
However,the current system of atomic masses is based on carbon-$12$ as the standard,which was agreed upon in $1961$.
Carbon-$12$ is an isotope of carbon represented as ${}^{12}C$.
In this system,${}^{12}C$ is assigned a mass of exactly $12$ atomic mass units $(amu)$,and the masses of all other atoms are determined relative to this standard.
One atomic mass unit $(amu)$ is defined as a mass exactly equal to $\frac{1}{12}$ of the mass of one carbon-$12$ atom.
$1 \ amu = 1.66056 \times 10^{-24} \ g$
The mass of a hydrogen atom is $1.6736 \times 10^{-24} \ g$.
Thus,in terms of $amu$,the mass of a hydrogen atom is $\frac{1.6736 \times 10^{-24}}{1.66056 \times 10^{-24}} \approx 1.0080 \ amu$.
Similarly,the mass of an oxygen-$16$ $({}^{16}O)$ atom is $15.995 \ amu$.
Currently,'$amu$' has been replaced by '$u$',which is known as unified mass.