Tc-99m<span> is a </span>metastable isomer<span> of </span>Tc-99. It finds widespread applications in <span>medical diagnostic procedures.
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Tc-99 is also a radioactive element. It's half-life is 2,11,000 years. Upon radioactive decay, it emits beta particles and gets converted into stable compound Ruthenium-99
This process of radioactive decay is shown below.
99 43Tc → 99 44Ru + 0 -1e
(stable) (β particle)
I'm not entirely sure but i think it's Se2-
Solids have a definite shape, and a definite volume.
Liquids have a definite volume, but have no definite shape.
Gas have neither a definite volume nor a definite shape.
Hope this helps!