a,
$m=65u=65.1,6605.10^{-27}=1,08.10^{-25}(kg)$
$r=1,35.10^{-1}(nm)=1,35.10^{-1}.10^{-9}=1,35.10^{-10}(m)$
$V=\dfrac{4}{3}\pi.r^3=\dfrac{4}{3}\pi.(1,35.10^{-10})^3=1,03.10^{-29}(m^3)$
$\Rightarrow D_{Zn}=\dfrac{m}{V}=10485,43(kg/m^3)$
b,
$r_{\text{hạt nhân}}=2.10^{-6}.10^{-9}=2.10^{-15}(m)$
$\Rightarrow V_{\text{hạt nhân}}=\dfrac{4}{3}\pi.(2.10^{-15})^3=3,35.10^{-44}(m^3)$
$\Rightarrow D_{\text{hạt nhân}}=\dfrac{m}{V}=3,22.10^{18}(kg/m^3)$
