Assertion: Boron can only form [BF4]-, whereas aluminium forms [AlF6]3-⋅ Reason: The first member of a group of elements in the s- and p- blocks shows anomalous behaviour.

Question

Assertion: Boron can only form [BF4]-, whereas aluminium forms [AlF6]3-⋅ Reason: The first member of a group of elements in the s- and p- blocks shows anomalous behaviour. (A) If both assertion and reason are true and reason is the correct explanation of assertion. (B) If both assertion and reason are true but reason is not the correct explanation of assertion. (C) If assertion is true but reason is false. (D) If both assertion and reason are false.

Tardigrade Admin · Accepted Answer

The maximum covalency of first member of each group of s- and p-block elements is 4, (due to non availability of d-orbitals) whereas the other members can expand their valence shell to accommodate more than four pairs of electrons (due to availability of d-orbitals).

Q. Assertion : Boron can only form $[B F_{4}]^{-}$ , whereas aluminium forms $[A l F_{6}]^{3 -} \cdot$
Reason: The first member of a group of elements in the $s -$ and $p$ - blocks shows anomalous behaviour.

If both assertion and reason are true and reason is the correct explanation of assertion.

If both assertion and reason are true but reason is not the correct explanation of assertion.

If assertion is true but reason is false.

If both assertion and reason are false.

The maximum covalency of first member of each group of $s$ - and $p$ -block elements is $4$ , (due to non availability of $d$ -orbitals) whereas the other members can expand their valence shell to accommodate more than four pairs of electrons (due to availability of $d$ -orbitals).

Q. Assertion : Boron can only form [BF4​]−, whereas aluminium forms [AlF6​]3−⋅ Reason: The first member of a group of elements in the s− and p- blocks shows anomalous behaviour.