By Avogadro’s Law

1 mole of carbon contain 6.023×10²³ carbon atoms = 12g of Carbon

6.023×10²³ atoms of carbon → 12g of Carbon

1 atom of Carbon → X g of Carbon

X = [12]/ 6.023×10²³

= 1.992×10^-23g of Carbon

Therefore, mass of 1 atom of Carbon is 1.992×10^-23g.