This is because they have three valence electrons that they can lose to achieve a stable noble gas configuration.
However, it's important to note that:
* Boron often forms compounds with an oxidation state of +3, but it can also form compounds with oxidation states of +1 and +2.
* Thallium can also exhibit a +1 oxidation state due to the inert pair effect (the reluctance of the ns² electrons to participate in bonding).
Therefore, while +3 is the most common oxidation state for group 13 elements, it's not the only one they can adopt.
