Em tham khảo nha:

\(\begin{array}{l}
{n_{KN{O_3}}} = \dfrac{m}{M} = \dfrac{a}{{101}}\,mol \Rightarrow {n_O} = \dfrac{a}{{101}} \times 3 = \dfrac{{3a}}{{101}}\,mol\\
{n_{CaC{O_3}}} = \dfrac{m}{M} = \dfrac{a}{{100}} \Rightarrow {n_O} = \dfrac{a}{{100}} \times 3 = \dfrac{{3a}}{{100}}\,mol\\
{n_{NaHC{O_3}}} = \dfrac{m}{M} = \dfrac{a}{{84}} \Rightarrow {n_O} = \dfrac{a}{{84}} \times 3 = \dfrac{a}{{28}}\,mol\\
{n_{MgSi{O_3}}} = \dfrac{m}{M} = \dfrac{a}{{100}} \Rightarrow {n_O} = \dfrac{a}{{100}} \times 3 = \dfrac{{3a}}{{100}}\,mol\\
 \Rightarrow\text{ Số nguyên tử Oxi:} NaHC{O_3} > CaC{O_3} = MgSi{O_3} > KN{O_3}
\end{array}\)