a)
$m_{C}$=$m_{p}$ +$m_{n}$+$m_{e}$=$6×1,6726×10^{-27}$ ++$6×9,1094×10^{−31}$
+$6×1,6748×10^{−27}$
⇒$M_{C}$=2,009×$10^{−26}$kg
b)$m_{e}=$6×9,1094×10^{−31}$=$5,466×10^{−30}$kg
$\frac{m_{e}}{m_{C}}$ =$\frac{5,466×10^{−30}}{2,009×10^{−26}}=$2,72×10^{−4}$≈0
XIN TLHN Ạ