The new isotope of oxygen raises doubts about its behavior. Oxygen-28 has the largest known number of neutrons in the nucleus of an oxygen atom.

Scientists expected it to be stable, but unexpectedly it turned out to be unstable; which refutes the concept of “magic” numbers of particles in a nuclear atom. The nucleus of an atom contains subatomic particles called nucleons, which include protons and neutrons. The atomic number of an element is determined by the number of protons, but the number of neutrons can vary.

Isotopes of elements with different numbers of neutrons are called isotopes. Previously, the maximum number of neutrons in an oxygen isotope was 18 in oxygen-26 (8 protons plus 18 neutrons equals 26 nucleons). But a team led by nuclear physicist Yosuke Kondo of the Tokyo Institute of Technology discovered two new isotopes of oxygen: oxygen-27 and oxygen-28 with 19 and 20 neutrons.

The research was conducted at the RIKEN Radioactive Isotope Beam Factory, a cyclotron-type accelerator designed to create unstable isotopes. In the research, the team irradiated calcium-48 isotopes to a beryllium target, producing lighter atoms, including fluorine-29, the fluorine isotope with 9 protons and 20 neutrons. Fluorine-29 then collided with the liquid hydrogen target to split a proton and form oxygen-28.

The experiment was successful but the result was unexpected. Both oxygen-27 and oxygen-28 were found to be unstable, existing only for a moment before oxygen-24 and decayed into 3 or 4 free neutrons. Oxygen-28 is particularly interesting because 8 and 20 are the “magic” numbers for protons and neutrons, respectively, which indicates its stability.

In nuclear physics, the term “magic number” refers to the number of nucleons that completely fill a shell, and each new shell differs from the previous one by a significant energy difference. An atomic nucleus with proton and neutron shells containing magic numbers is known as double magic and is considered particularly stable. Source