# Spin-$\frac{1}{2}$ particles in chemistry

Electrons and protons are spin-$\frac{1}{2}$ particles, so under a rotation by 360$^\circ$, their wavefunction changes by a sign. They are also commonly found alone in chemical reactions, especially protons (H$^+$ ions). Does this 720$^\circ$ rotation-invariance property have any important effects on chemistry?

When we talk about rotating an electron, or any fermion, we are not talking about a physical rotation in the sense of rotating any macroscopic body. ACuriousMind explains this very clearly here. So the rotational properties of the fermion wavefunction have no direct physical relevance to chemistry. If you rotate an electron by $2\pi$ it's still the same electron.