Em tham khảo nha :
\(\begin{array}{l}
a)\\
\text{Số hạt không mang điện chiếm 35%}\\
n = \dfrac{{35 \times 40}}{{100}} = 14\\
2p + n = 40 \Rightarrow p = \dfrac{{40 - 14}}{2} = 13\\
\Rightarrow A:\text{Nhôm}(Al)\\
b)\\
{m_{Al}} = 13 \times 1,6726 \times {10^{ - 24}} + 13 \times 9,1094 \times {10^{ - 28}} + 14 \times 1,6748 \times {10^{ - 24}}\\
{m_{Al}} = 4,52 \times {10^{ - 23}}g\\
{m_{3Al}} = 3 \times 4,52 \times {10^{ - 23}} = 1,356 \times {10^{ - 22}}g\\
c)\\
{m_{Na}} = 11 \times 1,6726 \times {10^{ - 24}} + 11 \times 9,1094 \times {10^{ - 28}} + 12 \times 1,6748 \times {10^{ - 24}}\\
{m_{Na}} = 3,85 \times {10^{ - 23}}g\\
{m_{Na}} < {m_{Al}}
\end{array}\)