Nuclear decay

A nucleus that is unstable drops on its own into a lower-energy arrangement. Nothing hits it. The leftover pieces weigh slightly less, and that missing mass becomes energy ($E = mc^2$).

This lesson has four articles, in order:

1. Balancing equations — the math side. Mass number, atomic number, charge. Alpha, beta-minus, beta-plus, electron capture.
2. Mechanisms — what actually happens, step by step. Start with alpha, then the two betas, then electron capture. Gamma is left out here.
3. Half-life — what half-life means and how to calculate it, from simple fractions up to logs.

You do not need any physics background. Every diagram uses the same colours throughout: red for protons, gray for neutrons, blue for electrons.