* Variable Oxidation States: Transition metals are known for having multiple oxidation states. This means they can lose a varying number of electrons depending on the chemical environment they're in.

* Electron Configuration: Their electron configuration involves partially filled d-orbitals, which allows them to readily lose electrons from both their s and d orbitals.

* Examples:

* Iron (Fe) can have oxidation states of +2 (losing 2 electrons) or +3 (losing 3 electrons).

* Copper (Cu) can have oxidation states of +1 (losing 1 electron) or +2 (losing 2 electrons).

General Trends:

* Group 3-7: These metals typically lose electrons from their 4s orbital first, then from their 3d orbital.

* Group 8-10: These metals tend to lose electrons from both their 4s and 3d orbitals simultaneously.

* Group 11-12: These metals primarily lose electrons from their 4s orbital.

It's important to remember that the number of electrons a transition metal loses depends on the specific chemical reaction and the resulting compound.