Question

WRITE THE ANOMALOUS PROPERTIES OF BORON

Answer 1

Anomalous Properties of Boron

Though aluminum is a metal, Boron is a non-metal.

Aluminium is a good conductor of electricity but Boron is not.

Boron exists in two structures amorphous and crystalline. Aluminum is a delicate metal and does not exist in various structures.

The boiling point and melting point of boron are much higher as compared to those of aluminum.

Boron frames just covalent compounds while aluminum shapes even some ionic compounds.

The oxides and hydroxides of boron are acidic in nature though those of aluminum are amphoteric.

The trihalides boron (BX3) are monomers whereas, aluminum halides subsists as dimers (Al2X6).

The hydrides of boron are quite inert while those of aluminum are flimsy.

Answer 2

Anomalous Properties of Boron :

The trichloride, bromides, and iodides of all these elements being covalent in nature are hydrolysed in water, species like tetrahedral $\mathsf{{[M(OH) _4]}^{-4}}$ and octahedral $\mathsf{{[M(H_{2}O)_6]}^{3+}}$, except in Boron, exist in aqueous medium.

It  is due to the absence of d - orbitals that the maximum covalence of Boron is 4. Since, the d- orbitals are available with Aluminium and other elements, the maximum covalence can be expected beyond 4.

The main reasons for the anomalous nature :

⚫Exceptionally small in size.

⚪High Ionisation Enthalpy

⚫Absence of d - orbitals in it's valence shell.