The total for if4- valence electrons is set by counting valence electrons from iodine and fluorine and then adjusting for the overall negative charge on IF4−. That total controls how many bonding pairs and lone pairs appear in the Lewis structure and predicts the VSEPR molecular shape.
Valence-electron sources in IF4−
Iodine is a Group 17 element with 7 valence electrons. Each fluorine atom is also Group 17 with 7 valence electrons. The overall −1 charge contributes one additional electron to the total count.
IF4− contains 36 total valence electrons.
Electron placement consistent with octets and an expanded octet
Four I–F single bonds require \(4 \times 2 = 8\) electrons. After bonding, fluorine atoms are completed to octets with three lone pairs each (\(6\) electrons per F, \(24\) electrons total for four F). The remaining electrons reside on iodine as lone pairs.
Iodine therefore carries two lone pairs in addition to four bonding pairs, giving six electron domains around iodine. This exceeds an octet on the central atom and is categorized as an expanded-octet Lewis structure, which is permitted for iodine (period 5).
Formal charges in the dominant Lewis structure
Formal charge bookkeeping confirms the placement: each fluorine is neutral, and the negative charge resides on iodine in the simplest single-bond structure.
| Atom | Valence electrons | Nonbonding electrons | Bonding electrons | Formal charge \(=\;V - (N + \tfrac{B}{2})\) |
|---|---|---|---|---|
| I | 7 | 4 (two lone pairs) | 8 (four single bonds) | \(7 - (4 + \tfrac{8}{2}) = 7 - (4 + 4) = -1\) |
| F (each) | 7 | 6 (three lone pairs) | 2 (one single bond) | \(7 - (6 + \tfrac{2}{2}) = 7 - (6 + 1) = 0\) |
VSEPR geometry and molecular shape
Six electron domains around iodine correspond to an octahedral electron-domain geometry. With four bonding domains and two lone-pair domains, the VSEPR classification is AX4E2. The two lone pairs occupy opposite axial positions (trans), leaving the four I–F bonds in a single plane.
Electron-domain geometry: octahedral (6 domains). Molecular shape: square planar (AX4E2).
Common counting errors
A missing electron from the −1 charge shifts the total from \(36\) to \(35\) and forces an incorrect odd-electron Lewis structure. Another frequent mistake is placing three lone pairs on iodine after completing fluorine octets; the remaining-electron count after the four fluorine octets is \(4\) electrons, which corresponds to exactly two lone pairs on iodine.
Direct conclusion
IF4− contains \(36\) valence electrons in total; the Lewis structure places four single I–F bonds, three lone pairs on each fluorine, and two lone pairs on iodine, giving an octahedral electron-domain geometry and a square-planar molecular shape (AX4E2).