El movimiento de las placas tectónicas
Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2<span>) electrons.</span>
It's a combination of substances that does not have uniform composition and properties.
Since substances break down much faster under aerobic conditions, as oxygen helps break the molecules apart, in a process called oxidation, biodegradation that actually takes place does so slowly that effects may not be visible in decades after a product was buried, if even then.