NEETChemistryChemical Bonding and Molecular Structure
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The central iodine atom in the triiodide ion ( I ₃^- ) has an expanded octet with 12 electrons in its valence shell. Reason (R): The central iodine atom in I ₃^- forms two single bonds with terminal iodine atoms and retains three lone pairs of electrons. In the light of the above statements, choose
Options
- ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
- CAssertion (A) is true but Reason (R) is false.
- DAssertion (A) is false but Reason (R) is true.
Correct answer
D. Assertion (A) is false but Reason (R) is true.
Step-by-step solution
In the triiodide ion ( I ₃^- ), the central iodine atom has 7 valence electrons. The negative charge adds 1 more electron, giving a total of 8 electrons available for bonding and lone pairs. The central iodine forms two single bonds with the two terminal iodine atoms, utilizing 2 electrons. The remaining 6 electrons form 3 lone pairs. The total number of electrons in the valence shell of the central iodine atom is the sum of electrons in bond pairs and lone pairs: (2 2) + (3 2) = 4 + 6 = 10 electrons. Therefore, th