Can someone explain to me, what does Metastable isotope means?
I already read the definitions on the internet but I really don't understand it.
Thanks in advance.
I wish I knew your educational level. I will assume undergraduate.
Remember the shell model for electrons in an atom?
Well, the nucleus nucleons occupy energy levels also, they have energy levels, and quantum numbers very similar to the electron shells.
Nucleons all occupy ground levels, but as electrons can be, they can be excited to higher energy states. The occupancy of these different states changes some of the characteristics of the nucleus itself and one of these characteristics is nuclear stability. The so called metastable isotopes are energy variants of specific isotopes which are unstable, but it turns out, the excited state configuration may be 1000 times more stable than the ground state nucleus. These are called metastable isotopes.
http://en.wikipedia.org/wiki/Nuclear_orbital
How about TC-99m? it is a metastable isotope, but the half life is 6hours. it is said that metastable isotope has lived longer than isotopes in a stable stae
I don't get that part.
Of course! Let me explain what a metastable isotope means in a simpler way for you.
When we talk about atoms, they have a specific number of protons and neutrons in their nucleus. Isotopes are different forms of the same element that have the same number of protons but a different number of neutrons.
Now, a metastable isotope refers to an isotope that has a longer lifetime in an excited state than other isotopes. Excited states occur when an atom gains some extra energy and its electrons move to higher energy levels. Normally, atoms quickly lose this energy and return to their stable ground state.
However, certain isotopes can retain this excess energy for longer periods. These isotopes exist in what we call a metastable state, where they remain in an excited state for an extended period before returning to their ground state.
The reason for their long-lived excited state can vary. It could be due to a particular arrangement of protons and neutrons, making it more stable in that higher energy state. Sometimes, it may be difficult for these isotopes to release the excess energy due to specific quantum rules or limited pathways available for energy release.
To give you a practical example, one commonly known metastable isotope is technetium-99m (Tc-99m). It's used in medical imaging because it emits gamma rays, which can be detected by special cameras. Tc-99m remains in its excited state for a short time before emitting these gamma rays and returning to a stable state.
So, in summary, metastable isotopes are isotopes that have a longer lifetime in an excited state compared to other isotopes. Their ability to retain excess energy can have different applications and implications in various scientific fields.