For a rough estimate of nuclear stability

PHYSICS · Single correct · A Level · Physics · Nuclear physics · Nuclear physics

Problem

For a rough estimate of nuclear stability, take the attractive energy as

E_n = 16A\,\text{MeV}

and the repulsive Coulomb energy as

E_c = 0.7\,\dfrac{Z^{2}}{A^{1/3}}\,\text{MeV}

. For which one of the following nuclei does the ratio

E_c/E_n

most nearly reach or exceed

0.25

, indicating the greatest tendency toward spontaneous fission? (a)

{}^{120}_{50}\text{Sn}

(b)

{}^{208}_{82}\text{Pb}

(c)

{}^{238}_{92}\text{U}

(d)

{}^{56}_{26}\text{Fe}