1. Sửa đề: $26p$, $26e$, $30n$
$m_n=30.1,67.10^{-24}=5,01.10^{-23}(g)$
$m_p=26.1,67.10^{-24}=4,342.10^{-23}(g)$
$m_e=30.9,1.10^{-28}=2,73.10^{-26}(g)$
$\Rightarrow m_{Fe}=m_p+m_n+m_e=9,35.10^{-23}(g)$
2.
Trong $9,35.10^{-23}g$ sắt có $2,73.10^{-26}g$ electron.
$\Rightarrow 1000g$ sắt có:
$m_e=\dfrac{2,73.10^{-26}.1000}{9,35.10^{-23}}=0,292g$