CHEMISTRY COMMUNITY

Why is the shape of an i3- ion linear not angular? Don't the two lone pairs on top of the central iodine repel the other two iodine atoms from being attached in a straight line to the central iodine to bent?

I3- ions have three lone pairs around the central I atom, meaning the molecule as a whole has an electron geometry of trigonal bipyramidal and a linear molecular geometry.

It's easier to understand why it's linear if you imagine a bipyramidal structure. Since there are three lone pairs in the I3- ion, imagine that the three central atoms of the bipyramidal structure are removed, leaving only the top, middle, and bottom atoms in a linear formation.