How to Draw the Lewis Structure for the I3+ Ion and Describe Its Molecular Geometry

To draw the Lewis structure for the I₃⁺ ion and describe its molecular geometry, follow these steps:

1. Count the Total Number of Valence Electrons:
   • Iodine (I) has 7 valence electrons.
   • Since there are three iodine atoms, the total number of valence electrons is 3 × 7 = 21.
   • However, the I₃⁺ ion has a positive charge, which means it has lost one electron. Therefore, the total number of valence electrons is 21 – 1 = 20.
2. Determine the Central Atom:
   • In the I₃⁺ ion, the central atom is the middle iodine atom.
3. Draw the Skeleton Structure:
   • Place the central iodine atom in the middle and connect it to the other two iodine atoms with single bonds.
4. Distribute the Remaining Electrons:
   • After forming the single bonds, you have used 4 electrons (2 for each bond).
   • You have 16 electrons left to distribute as lone pairs.
   • Place three lone pairs on each of the outer iodine atoms and two lone pairs on the central iodine atom.
5. Check the Octet Rule:
   • Each iodine atom should have 8 electrons around it (either in bonds or lone pairs).
   • In this structure, each iodine atom satisfies the octet rule.
6. Determine the Molecular Geometry:
   • The I₃⁺ ion has a linear molecular geometry.
   • This is because the central iodine atom is bonded to two other iodine atoms, and there are no lone pairs on the central atom that would cause a deviation from linearity.

In summary, the Lewis structure for the I₃⁺ ion consists of three iodine atoms with the central iodine atom bonded to the other two. The molecular geometry is linear.