In the case of boron (B2), where two boron atoms come together to form a molecule, each boron atom contributes three valence electrons. When the two boron atoms share their electrons, they form a covalent bond, sharing a total of six electrons.
While it is true that boron typically forms compounds by sharing electrons and can satisfy the octet rule by sharing additional electrons, it's important to note that boron does not readily form compounds where it achieves a complete octet. Boron is an exception to the octet rule due to its electron configuration and bonding tendencies.
Boron's atomic electron configuration is 1s2 2s2 2p1, meaning it has only three valence electrons in its outer energy level. When boron forms compounds, it tends to have incomplete octets. It is commonly found in compounds where it shares fewer than eight electrons, such as boron trifluoride (BF3), which forms three covalent bonds, or boron trichloride (BCl3), which also forms three covalent bonds.
In the case of B2, the molecule remains stable with the shared six valence electrons, even though it does not fulfill the octet rule. The bonding in B2 involves a molecular orbital model, and the stability arises from the sharing of electrons between the two boron atoms rather than achieving an octet.
In summary, boron does not typically pull in additional electrons to satisfy the octet rule. Its tendency to form compounds with incomplete octets is due to its electron configuration and unique bonding patterns.