Calculate the number of atoms in each of the following:
$(i)$ $52$ moles of $Ar$
$(ii)$ $52$ $u$ of $He$
$(iii)$ $52$ $g$ of $He$.

(N/A) $(i)$ $1$ mole of $Ar = 6.022 \times 10^{23}$ atoms of $Ar$
$\therefore 52$ mol of $Ar = 52 \times 6.022 \times 10^{23}$ atoms of $Ar = 3.13144 \times 10^{25}$ atoms of $Ar$
$(ii)$ $1$ atom of $He = 4$ $u$ of $He$
$4$ $u$ of $He = 1$ atom of $He$
$1$ $u$ of $He = \frac{1}{4}$ atom of $He$
$52$ $u$ of $He = \frac{52}{4}$ atoms of $He = 13$ atoms of $He$
$(iii)$ $4$ $g$ of $He = 6.022 \times 10^{23}$ atoms of $He$
$\therefore 52$ $g$ of $He = \frac{6.022 \times 10^{23} \times 52}{4}$ atoms of $He = 7.8286 \times 10^{24}$ atoms of $He$