Draw the Lewis structure for IF4 in the window below and then answer the questions that follow.

The Correct Answer and Explanation is:

Let’s first clarify the molecule you asked about: IF4. Actually, the typical stable molecule involving iodine and fluorine is IF4⁻ (tetrafluoroiodide ion), not IF4 neutral molecule. So I will assume you meant IF4⁻ because IF4 neutral is very unusual and probably unstable.

Step 1: Count the total valence electrons

Iodine (I) is in group 17 and has 7 valence electrons.
Fluorine (F) is in group 17 and has 7 valence electrons.
There are 4 fluorines: 4 × 7 = 28 valence electrons.
The extra negative charge (⁻) adds 1 more electron.

Total valence electrons = 7 (I) + 28 (4 F) + 1 (extra electron) = 36 valence electrons

Step 2: Draw the skeleton structure

Put iodine in the center (less electronegative than fluorine).
Attach the 4 fluorines around iodine with single bonds.

Each single bond counts as 2 electrons.

4 bonds × 2 e⁻ = 8 electrons used.
Remaining electrons = 36 – 8 = 28 electrons.

Step 3: Distribute remaining electrons to complete octets

Complete the octet of each fluorine first:
- Each fluorine needs 6 more electrons (3 lone pairs) to complete its octet.
- 4 F × 6 e⁻ = 24 electrons.
Subtract 24 electrons from the remaining 28:
- 28 – 24 = 4 electrons left.

Step 4: Place leftover electrons on iodine

The remaining 4 electrons (2 lone pairs) are placed on iodine.

Step 5: Check formal charges

Iodine has 4 bonds (8 bonding electrons) + 4 lone electrons = 12 electrons around it.
This is possible because iodine is in period 5 and can have an expanded octet.

Formal charges:

For Iodine: Valence electrons = 7
- Nonbonding electrons = 4
- Bonding electrons = 8 (4 bonds × 2 e⁻ each)
- Formal charge = 7 – (4 + 8/2) = 7 – (4 + 4) = 7 – 8 = -1
For Fluorine: Valence electrons = 7
- Nonbonding electrons = 6
- Bonding electrons = 2 (1 bond × 2 e⁻)
- Formal charge = 7 – (6 + 2/2) = 7 – (6 +1) = 0

So the overall charge is -1, matching IF4⁻.

Summary Lewis structure for IF4⁻:

Iodine in center with 4 single bonds to fluorines.
Each fluorine has 3 lone pairs.
Iodine has 2 lone pairs.
Overall charge -1.

Explanation (300+ words)

The Lewis structure of the tetrafluoroiodide ion (IF4⁻) reflects fundamental principles of valence electrons and molecular geometry. Iodine, a halogen in period 5, can expand its octet to accommodate more than 8 electrons due to available d orbitals, which is crucial for forming stable hypervalent molecules. In IF4⁻, iodine bonds to four fluorine atoms. Each fluorine atom requires a complete octet, fulfilled by one bonding pair shared with iodine and three lone pairs.

Counting valence electrons starts with iodine’s 7 and fluorine’s 7 per atom, plus one extra electron for the negative charge, totaling 36 valence electrons. Four single bonds use 8 electrons; completing the octets of four fluorines uses 24 more. This leaves 4 electrons for iodine’s lone pairs, fulfilling the expanded octet. The formal charges confirm that the best Lewis structure places a -1 charge on iodine, with fluorines neutral, consistent with the ion’s overall charge.

The shape of IF4⁻, predicted by the VSEPR (Valence Shell Electron Pair Repulsion) theory, arises from the presence of two lone pairs on iodine and four bonding pairs to fluorine. These six electron pairs (4 bonding + 2 lone) adopt an octahedral arrangement to minimize repulsion. The lone pairs occupy axial positions, pushing the four fluorines into an equatorial plane, resulting in a square planar molecular geometry.

Understanding the Lewis structure helps predict the molecule’s shape, reactivity, and properties. For example, the negative charge on iodine influences its reactivity and interaction with other species. This structure also explains bond angles around 90°, typical for square planar molecules. In summary, constructing the Lewis structure of IF4⁻ involves balancing electron counts, formal charges, and the spatial arrangement of electron pairs, reflecting the fundamental chemistry of hypervalent halogen compounds.