AIIMS2018Chemistry-Coordination Compounds

AIIMS 2018 Chemistry Coordination Number MCQ Question

Type: MCQ-conceptual-Medium-Class 12

Assertion : Both Be\text{Be} and Al\text{Al} can form complexes such as BeF42\text{BeF}_4^{2-} and AlF63\text{AlF}_6^{3-} respectively. BeF63\text{BeF}_6^{3-} is not formed.

Reason : In case of Be\text{Be}, no vacant d-orbitals are present in its outermost shell.

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.

Correct Answer

Option A

Detailed Explanation

Beryllium (Be) has no vacant d-orbitals in its outermost shell, limiting its ability to expand its coordination number beyond four. Consequently, Be can form complexes like BeF₄²⁻, where it utilizes its available orbitals effectively, while aluminum (Al), with its vacant d-orbitals, can form AlF₆³⁻. However, BeF₆³⁻ is not feasible due to the lack of available orbitals for bonding, making option A correct. The other options are not relevant as they do not provide alternative explanations or correct structures.

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