Atomic weight of metal : 24
Further explanation
Proust states the Comparative Law that compounds are formed from elements with the same Mass Comparison so that compounds have a fixed composition of elements
Divalent metal oxide=XO
MW O = 16
MW XO₂ = X+16
[tex]\tt \%mass=\dfrac{Ar~X}{X+16}\times 100\%\\\\0.6=\dfrac{X}{X+16}\\\\0.6(X+16)=X\\\\0.6X+9.6=X\\\\0.4X=9.6\rightarrow X=24[/tex]
