Answer
$$
-23.0 \mathrm{\ MeV}
$$
Work Step by Step
if $M_{\mathrm{Cr}} \text { is the mass of a }^{52} \mathrm{Cr}$ nucleus
and $M_{\mathrm{Mg}} \text { is the mass of a }^{26} \mathrm{Mg}$ nucleus,
then disintegration energy is
$$
Q=\left(M_{\mathrm{Cr}}-2 M_{\mathrm{Mg}}\right) c^{2}$$ $$=[51.94051 \mathrm{u}-2(25.98259 \mathrm{u})](931.5 \mathrm{MeV} / \mathrm{u})=-23.0 \mathrm{MeV}
$$
