Technetium-99m (Tc-99m) is the most common isotope used in nuclear medicine. It undergoes isomeric transition to Technetium-99 (Tc-99), emitting a gamma ray. Here's the nuclear equation:

⁹⁹mTc → ⁹⁹Tc + γ

* ⁹⁹mTc: Technetium-99m (metastable state)

* ⁹⁹Tc: Technetium-99 (ground state)

* γ: Gamma ray

Explanation:

* Technetium-99m exists in an excited, metastable state, denoted by the "m" subscript.

* It decays to the ground state, Technetium-99, by releasing a gamma ray.

* The gamma ray has no mass or charge, so it doesn't affect the atomic or mass number of the Technetium.

This decay process is why Technetium-99m is useful in medical imaging. The gamma ray emitted can be detected by a scanner, allowing doctors to visualize specific organs and tissues.