The molecular geometry for ICl4- ________is and the approximate value of the Cl-I-Cl bond angle is
The Correct Answer and Explanation is:
Correct Answer:
The molecular geometry for ICl₄⁻ is square planar, and the approximate value of the Cl–I–Cl bond angle is 90 degrees.
Explanation
Iodine tetrachloride anion, denoted as ICl₄⁻, is a polyatomic ion consisting of one iodine atom and four chlorine atoms with a negative charge. To determine its molecular geometry and bond angles, the Valence Shell Electron Pair Repulsion (VSEPR) theory serves as a helpful guide. This theory is based on the repulsion between electron pairs surrounding a central atom, which shapes the molecule to minimize repulsive interactions.
First, consider the number of valence electrons around the central iodine atom. Iodine belongs to group 17 and contributes 7 valence electrons. Each chlorine atom contributes one electron via the I–Cl bond, and the ion carries an additional electron due to its negative charge, totaling 36 valence electrons (7 from I + 4×7 from Cl + 1 extra).
When constructing the Lewis structure, iodine forms four single bonds with four chlorine atoms. This accounts for 8 electrons used in bonding. The remaining electrons are arranged as lone pairs. Iodine, being in Period 5, can expand its octet. After satisfying the octets of chlorine atoms, there are two lone pairs left on the central iodine atom.
With four bonded atoms and two lone pairs on the central atom, the steric number is 6. According to VSEPR theory, a steric number of 6 corresponds to an octahedral electron geometry. However, the two lone pairs occupy axial positions to reduce repulsion, resulting in a square planar molecular geometry.
The bond angles in an ideal square planar geometry are approximately 90 degrees between adjacent Cl–I–Cl atoms. These angles remain close to ideal because the lone pairs are located opposite each other and do not distort the square plane significantly. Thus, ICl₄⁻ has a square planar shape with Cl–I–Cl bond angles around 90°.
