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In chemistry, chemical stability is the thermodynamic stability of a chemical system, in particular a chemical compound or a polymer. [1]Thermodynamic stability occurs when a system is in its lowest energy state, or in chemical equilibrium with its environment.
Stable stratification of fluids occurs when each layer is less dense than the one below it. Unstable stratification is when each layer is denser than the one below it. Buoyancy forces tend to preserve stable stratification; the higher layers float on the lower ones. In unstable stratification, on the other hand, buoyancy forces cause convection ...
If a nucleus can be split into two parts that have a lower total energy (a consequence of the mass defect resulting from greater binding energy), it is unstable. The nucleus can hold together for a finite time because there is a potential barrier opposing the split, but this barrier can be crossed by quantum tunneling .
A metastable state of weaker bond (1), a transitional "saddle" configuration (2) and a stable state of stronger bond (3). In chemistry and physics, metastability is an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability.
An even number of protons or neutrons is more stable (higher binding energy) because of pairing effects, so even–even nuclides are much more stable than odd–odd. One effect is that there are few stable odd–odd nuclides: in fact only five are stable, with another four having half-lives longer than a billion years. [citation needed]
The least stable is 10 He, with half-life 260(40) yoctoseconds (2.6(4) × 10 −22 s), though 2 He may have an even shorter half-life. In Earth's atmosphere, the ratio of 3 He to 4 He is 1.343(13) × 10 −6. [5] However, the isotopic abundance of helium varies greatly depending on its origin.
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Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reactants or reagents .