Boron ($B$) exhibits anomalous behavior compared to $Al,Ga,In,Tl$ due to its exceptionally small size.

• Properties:

1. Non-metallic: Boron is a metalloid/non-metal, while all other group members are metals.
2. Covalent Bonding: Due to its high ionization energy and small size, it does not form $B^{3+}$ ions readily and forms covalent bonds.
3. Octet Rule: Boron lacks $d$-orbitals in its valence shell (max covalency is $4$). It cannot expand its octet to match the coordination numbers ($6$ or more) seen in heavier members like $[Al{F}_6{]}^{3-}$.