To calculate the total number of atoms in 3 NH4CI, we need to multiply the number of atoms in one molecule of NH4CI by 3.

One molecule of NH4CI contains 1 nitrogen atom, 4 hydrogen atoms, and 1 chlorine atom. So, the total number of atoms in one molecule of NH4CI is 1 + 4 + 1 = 6.

Therefore, the total number of atoms in 3 NH4CI is 6 x 3 = 22.