Klaus Blaum

An electron inside a molecule behaves like a tiny magnet, and its 'strength' can be measured with enormous precision. Physicists took the molecular ion HD⁺ — a nucleus made of a proton and a deuteron (heavy hydrogen), with a single electron circling around it — and placed it in a strong magnetic field of 4 teslas (roughly 80,000 times stronger than…

The atomic nucleus is not a bag of marbles but an ordered structure where protons and neutrons fill shells, much like electrons in an atom. When a shell is filled, the nucleus becomes especially stable, and the number of particles is called magic. For calcium with 20 protons, the classic magic neutron numbers are 20 and 28.