JEE Main · 2021 · 20 Jul 2021 · Shift 1 · Chemical Bonding and Molecular Structure

The number of lone pairs of electrons on the central I atom in

I_{3}^{-}

is ____.

Answer: 3

Solution

The triiodide ion is formed when a molecule of

I_{2}

accepts an iodide ion, so the central atom is an iodine bonded to two terminal iodine atoms. Around that central atom are its own seven valence electrons together with the extra electron carried by the negative charge, and two of these eight are spent in the two

I - I

bonds. The six that remain stay as three lone pairs; they take the equatorial positions of a trigonal bipyramidal arrangement of five electron pairs, which leaves the ion linear. The central iodine atom carries 3 lone pairs.

JEE Main · 2021 · 20 Jul 2021 · Shift 1 · Integer answer

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