
All beings, great and small, have their ways of finding balance. The sun regulates the rate of nuclear reactions; cells adjust the metabolism to meet changing needs. Mammals maintain their favored body temperature. And the ways in which temperature can be controlled by ecosystems are mind boggling!
Existing is a big deal. And existing permanently is huge. Even for something as tiny as the atomic nucleus.
The nucleus consists of two types of particles: neutrons and protons. They are held together by nuclear forces. However, not all combinations of neutrons and protons will form a stable nucleus. Most either fall apart quickly or have no chance of existing at all. Anyway, one thing at a time.
A single proton—a particle with a positive electric charge—exists permanently, and independently constitutes a hydrogen nucleus. But a single neutron—devoid of electric charge—is an ephemeron that survives for about fifteen minutes before breaking apart. Two protons cannot be paired, nor do two neutrons stick together. The only stable pair is a proton plus a neutron. When it comes to trios, only two protons and a neutron have a chance of surviving together long-term. Three protons is absurd, three neutrons a whim of the imagination, and two neutrons plus one proton last about twelve years and four months (statistically, this is a half-life).
As for the quartets, only one is stable: two neutrons plus two protons. The other four combinations are either impossible to realize or fall apart in the blink of an eye. As more neutrons and protons (or nucleons, as they are collectively called) are added, increasingly impossible or volatile configurations emerge. The stable and trustworthy among them become ever rarer exceptions.
When the number of protons is represented on the horizontal axis and the number of neutrons