Is ICl2- nonpolar or polar?

1 Answer
Aug 4, 2016

Nonpolar. Its dipoles all cancel.


Never really heard of ICl2, but since it's more probable than ICl2...

To draw the Lewis structure, each halogen contributes 7 valence electrons, and the charge contributes 1. So we have 7+7+7+1=22 valence electrons.

Hence, we can distribute 6 on each Cl and 2 per single bond for a total of 6+6+2+2=16, putting the remaining 6 on iodine.

The hypothetical VSEPR-predicted structure would look like this:

Since the electron geometry was trigonal bipyramidal (5 electron groups), the molecular geometry is triatomic linear.

(Taking away atoms from a trigonal bipyramidal molecular geometry, you would get, in order, see-saw, T-shaped, triatomic linear, then diatomic linear.)

Since:

  • The molecule has two identical non-central atoms.
  • The structure is linear, giving dipoles that are opposite in direction to each other.
  • The three lone pairs of electrons are 120 away from each adjacent one, a rotationally-symmetric configuration; so, the lone-pair-bonding-pair repulsions sum to cancel out as well.

...it doesn't matter what the electronegativity difference is between Cl and I; the dipoles all cancel out to give a net dipole moment of 0 in all directions.

Therefore, ICl2 is projected to be nonpolar.


NOTE: Although iodine is less electronegative, it has to hold the 1 formal charge (but it would have a +1 oxidation state, while each Cl holds a 1 oxidation state and a 0 formal charge).

Since the only way to rework formal charges is to form a double bond using one of Cl's lone pairs (giving a 2 formal charge to iodine and +1 to chlorine), it's most favorable as it is now.