1 mole of carbon atoms means 6.022 × 10²³ carbon atoms. In this case 1 mole of carbon atoms weighs 12 grams. This means that the mass of 6.022 × 10²³ atoms of carbon is 12 grams.

Now, 6.022 × 10²³ atoms of carbon have mass = 12 g

1 atom of carbon has mass = g

= 1.99 × 10^-23 g

Thus, the absolute mass of 1 atom of carbon is 1.99 × 10^-23 grams.