Đáp án+Giải thích các bước giải:

Ta có:

$m=M\cdot1,6605\cdot10^{-24}g$

$V=\dfrac{75}{100}\cdot\dfrac{m}{D}$

Mặt khác: $V=\dfrac43\pi r^3$

Với Fe:

$m_{Fe}=55,85\cdot1,6605\cdot10^{-24}$

$m_{Fe}\approx9,274\cdot10^{-23}g$

$V_{Fe}=\dfrac{75}{100}\cdot\dfrac{9,274\cdot10^{-23}}{7,87}$

$V_{Fe}\approx8,838\cdot10^{-24}cm^3$

$\dfrac43\pi r_{Fe}^3=8,838\cdot10^{-24}$

$r_{Fe}^3=\dfrac{3\cdot8,838\cdot10^{-24}}{4\pi}$

$r_{Fe}\approx1,283\cdot10^{-8}cm$

$r_{Fe}\approx1,283$ (Ăng-tơ-rông)

Với Au:

$m_{Au}=196,97\cdot1,6605\cdot10^{-24}$

$m_{Au}\approx3,271\cdot10^{-22}g$

$V_{Au}=\dfrac{75}{100}\cdot\dfrac{3,271\cdot10^{-22}}{19,32}$

$V_{Au}\approx1,270\cdot10^{-23}cm^3$

$\dfrac43\pi r_{Au}^3=1,270\cdot10^{-23}$

$r_{Au}^3=\dfrac{3\cdot1,270\cdot10^{-23}}{4\pi}$

$r_{Au}\approx1,447\cdot10^{-8}cm$

$r_{Au}\approx1,447$ (Ăng-tơ-rông)