What will be the mass of one atom of $^{12}C$ in grams?

The mass of a $^{12}C$ (carbon-$12$) atom is calculated using the molar mass and Avogadro's constant $(N_{A})$.
$1$ mole of $^{12}C$ atoms has a mass of $12 \ g$ and contains $6.022 \times 10^{23}$ atoms.
Therefore,the mass of $1$ atom of $^{12}C$ is given by:
$\text{Mass of one atom} = \frac{\text{Molar mass}}{N_{A}}$
$= \frac{12 \ g}{6.022 \times 10^{23}}$
$= 1.992648 \times 10^{-23} \ g \approx 1.99 \times 10^{-23} \ g$