Em tham khảo nha :
\(\begin{array}{l}
{}_8^{16}O\\
p = e = Z = 8\\
n = 16 - 8 = 8\\
{}_6^{12}C\\
p = e = Z = 6\\
n = 12 - 6 = 6\\
{}_{11}^{23}Na\\
p = e = Z = 11\\
n = 23 - 11 = 12\\
{}_{35}^{79}Br\\
p = e = Z = 35\\
n = 79 - 35 = 44\\
{}_{19}^{39}K\\
p = e = Z = 19\\
n = 39 - 19 = 20
\end{array}\)