Explanation:
(1) 4g of hydrogen = 4 mole of hydrogen atoms \( = 4 \times 6.023 \times {10^{23}}\,\,atoms\)
(2) 71.0 gm of chlorine \( = \frac{{71.0}}{{71.0}}\)
= 1 moleof chlorine
\( = 6.023 \times {10^{23}}\,\,atoms\)
(3) 127 gm of iodine =1 mole of I atoms \( = 6.023 \times {10^{23}}\,\,atoms\)
(4) 48.0 gm of magnesium \( = \frac{{48.0}}{{24.0}}\)
2 moles of Mg \( = 2 \times 6.023 \times {10^{23}}\,\,atoms\)
\(\therefore \) 4.0 gm \({H_2}\) has the largest number of atoms.