NEETChemistryClassification of Elements and Periodicity in Properties
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Aluminium can form the complex ion [AlF₆]³⁻ but boron cannot form [BF₆]³⁻ . Reason (R): Aluminium has 9 valence orbitals in its valence shell whereas boron has only 4 valence orbitals. In the light of the above statements, choose the most appropriate answer from the options given below:
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
Assertion (A) is correct: Aluminium belongs to the third period and can expand its covalency beyond 4 to form octahedral complexes like [AlF₆]³⁻ . Boron belongs to the second period and is restricted to a maximum covalency of 4 , so it cannot form [BF₆]³⁻ . Reason (R) is correct and explains (A): The valence shell of boron ( n=2 ) consists of only four orbitals (one 2s and three 2p ). Due to the absence of d -orbitals, its maximum covalency is 4 . The valence shell of aluminium ( n=3 ) contains nine orbitals (one 3