Answer
Number of $NH_4$ ions: $2.41\times10^{23}\ ions$
Number of $SO_4$ ions: $1.20\times10^{23}\ ions$
Number of N atoms: $2.41\times10^{23}\ atoms$
Number of H atoms: $9.63\times10^{23}\ atoms$
Number of S atoms: $1.20\times10^{23}\ atoms$
Number of O atoms: $4.82\times10^{23}\ atoms$
Work Step by Step
Unit refers to a single $(NH_4)_2SO_4$
Number of $NH_4$ ions: $0.20\ mol\times6.022\times10^{23}\ units/mol \times 2\ NH_4\ ions/unit= 2.41\times10^{23}\ ions$
Number of $SO_4$ ions: $0.2\ mol\times6.022\times10^{23}\ units/mol \times 1\ SO_4\ ion/unit= 1.20\times10^{23}\ ions$
Number of N atoms: $0.20\ mol\times6.022\times10^{23}\ units/mol \times 2\ N\ atoms/unit= 2.41\times10^{23}\ atoms$
Number of H atoms: $0.20\ mol\times6.022\times10^{23}\ units/mol \times 8\ H\ atoms/unit= 9.63\times10^{23}\ atoms$
Number of S atoms: $0.20\ mol\times6.022\times10^{23}\ units/mol \times 1\ S\ atoms/unit= 1.20\times10^{23}\ atoms$
Number of O atoms: $0.20\ mol\times6.022\times10^{23}\ units/mol \times 4\ O\ atoms/unit= 4.82\times10^{23}\ atoms$
