Like Li and Be, Boron – the first member of group 13 also shows anomalous behavior due to extremely low size and high nuclear charge/size ratio, high electronegativity and non-availability of d electrons. The main point of differences are,

(1) Boron is a typical non- metal whereas other members are metals.

(2) Boron is a bad conductor of electricity whereas other metals are good conductors.

(3) Boron shows allotropy and exists in two forms – crystalline and amorphous. Aluminum is a soft metal and does not exist in different forms.

(4) Like other non-metals, the melting point and boiling point of boron are much higher than those of other elements of group 13.

(5) Boron forms only covalent compounds whereas aluminum and other elements of group 13 form even some ionic compounds.

(6) The hydroxides and oxides of boron are acidic in nature whereas those of others are amphoteric and basic.

(7) The trihalides of boron (BX₃) exist as monomers On the other hand, aluminum halides exist as dimers (Al₂X₆).

(8) The hydrides of boron i.e. boranes are quite stable while those of aluminum are unstable.

(9) Dilute acids have no action on boron Others liberate H₂ from them.

(10) Borates are more stable than aluminates.

(11) Boron exhibit maximum covalency of four e.g., BH^–₄ ion while other members exhibit a maximum covalency of six e.g., [Al(OH)₆]^3-­.

(12) Boron does not decompose steam while other members do so.

(13) Boron combines with metals to give borides e.g. Mg₃B₂. Other members form simply alloys.

(14) Concentrated nitric acid oxidizes boron to boric acid but no such action is noticed other group members.

B + 3HNO₃ → H₃BO₃+ 3NO₂