Understanding NRT- Reading 1- 2 of 2- Radiogaphic Testing A

Isomers
Nuclei can have the same neutron-proton composition but not be identical;
one nucleus can contain more energy than the other. Two nuclei that have
the same composition but varying energy are known as isomers. An example
of a pair of isomers is shown below. Technetium-99 can exist in two energy
states; the higher of the two is a temporary state generally referred to as a
metastable state. The symbol for a nuclide in the metastable state is obtained
by adding the letter m to the mass number (Tc-99m). A nucleus in the
metastable state will eventually give off its excess energy and change to the
other isomer. Such isomeric transitions have an important role in nuclear
medicine and are discussed in detail later.
Charlie Chong/ Fion Zhang
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