Protons and neutrons are fermions.The nucleus of helium-4 contains two protons and two neutrons.Which of the following spin states are allowed for the nucleus of a helium-4 atom?
A)both protons spin up,both neutrons spin up
B)both protons spin up,both neutrons spin down
C)one proton and one neutron spin up and one proton and one neutron spin down
D)All are correct.
E)None are correct.

Question

Quizplus · Accepted Answer

The helium-4 nucleus is a composite particle and must obey the Pauli exclusion principle. The total spin of the nucleus must be an integer (boson), so the spins of the protons and neutrons must pair up to give a total spin of zero.

Protons and Neutrons Are Fermions