What will be the mass of one 12C atom in g?
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.