Ta có: \(\left\{{}\begin{matrix}p+e+n=76\\p=e\\n=1,166\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}3,166p=76\\p=e\\n=1,166\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}p=e=24\\n=28\end{matrix}\right.\)
\(\Rightarrow A=p+n=24+28=52\left(u\right)\)
\(KHNT:^{52}_{24}Cr\)