What Is the Electron Geometry of IF5? | VSEPR Shape Explained

IF5 places six electron groups around iodine in an octahedral arrangement, with one lone pair that leaves a square pyramidal molecular shape.

IF5 (iodine pentafluoride) shows up in bonding chapters because it looks “too full” at first glance. Iodine sits in the middle with five fluorines around it, and many students pause right there: how can iodine hold that many bonds?

The good news is that you can get the electron geometry in a repeatable way every time. No memorizing random shapes. You count electron groups, place them in the lowest-crowding pattern, then name the electron geometry. After that, you name the molecular shape by ignoring the lone pairs.

Electron Geometry Vs Molecular Shape

These two labels answer two different questions.

• Electron geometry tells how all electron groups arrange around the central atom. “Electron groups” means bonds plus lone pairs.
• Molecular shape tells the shape made by the atoms only. Lone pairs still push, yet they do not show up as corners of the shape name.

For IF5, the electron geometry is the “all groups” picture. The molecular shape is the “atoms only” picture. Keeping that split in your head prevents most mistakes on tests.

Electron Geometry Of IF5 In VSEPR Terms

VSEPR is short for valence-shell electron-pair repulsion. The idea is simple: regions of electron density spread out around the central atom to reduce crowding. A single bond counts as one region. A double or triple bond still counts as one region for geometry.

In IF5, iodine is the central atom. Each I–F bond is one electron group. Iodine also carries one lone pair. That makes six electron groups total.

Step 1: Count Valence Electrons

Start by counting valence electrons for the whole molecule.

• Iodine is in Group 17, so it brings 7 valence electrons.
• Each fluorine is in Group 17, so each brings 7 valence electrons.
• Five fluorines bring 5 × 7 = 35 valence electrons.

Total valence electrons: 7 + 35 = 42.

Step 2: Sketch A Lewis Structure That Matches The Count

Place iodine in the center and connect five fluorines with single bonds. That uses 5 bonds × 2 electrons per bond = 10 electrons.

Give each fluorine an octet. Each F already has 2 electrons in its bond to iodine, so it needs 6 more as lone-pair electrons. For five fluorines, that uses 5 × 6 = 30 electrons.

So far you have used 10 + 30 = 40 electrons. You started with 42, so 2 electrons remain. Those two electrons sit on iodine as one lone pair.

Step 3: Turn The Lewis Picture Into Electron Groups

Now stop thinking about “electrons” and switch to “groups.” For VSEPR, you only care about how many regions of electron density surround iodine.

• Five I–F single bonds → 5 bonding groups
• One lone pair on iodine → 1 nonbonding group

That gives a steric number of 6 (5 + 1).

Step 4: Match Steric Number To Electron Geometry

Steric number 6 maps to an octahedral electron geometry. In an octahedral arrangement, six electron groups point toward the corners of an octahedron: four around the middle like a square, plus one above and one below.

If you like the AXE shorthand, IF5 is AX5E: A = iodine, X = five fluorines, E = one lone pair. AX5E sits under the steric-number-6 row, so it uses the octahedral electron arrangement.

Why The Molecular Shape Becomes Square Pyramidal

Once you know the electron geometry, naming the molecular shape is a clean move: remove the lone pair from the picture and name what the atoms form.

In an octahedral set, the two positions that sit above and below the square plane are called axial positions. The four positions in the square plane are equatorial. A lone pair takes one position, and it pushes harder than a bond pair does, so it “claims” space.

With steric number 6, putting the lone pair in an axial site leaves five fluorines arranged as a square base plus one atom above the base. That atom layout is a square pyramidal molecular shape.

This is the same logic used for BrF5 and ClF5, which share the same AX5E pattern.

Bond Angles You Should Expect

Ideal octahedral angles are 90° between adjacent positions and 180° between opposite positions. In real molecules with lone pairs, angles shift a bit because lone pairs repel more strongly than bonding pairs.

So, in IF5 you still think “mostly 90°,” yet you should allow for slight compression of some F–I–F angles near the lone pair on drawings and in answer choices.

Polarity Check In One Minute

Square pyramidal shapes are not perfectly symmetric. The fluorines pull electron density toward themselves, and the lone pair creates an uneven distribution. That means IF5 is polar as a molecule.

What “Lone Pair” Means Here

A lone pair is a pair of valence electrons located on one atom that does not form a bond. The definition is plain and consistent across texts, and it matters for VSEPR because lone pairs take space even when they are not visible as atoms in the final shape name. The IUPAC Gold Book definition of a lone pair gives the formal wording.

In IF5, the lone pair sits on iodine. It is counted as one electron group, just like one bond is counted as one electron group. That is why you get six groups even though you only see five atoms around iodine.

Common Misreads That Throw Off IF5 Geometry

Mixing Up Electron Count With Electron Groups

Students sometimes see “42 electrons” and assume the geometry must be tied to that number. Geometry does not use the raw electron total. It uses the count of regions around the central atom after you draw the Lewis structure.

Forgetting That Each Bond Counts Once

Even if a central atom forms a double bond in some molecule, that double bond counts as one region for VSEPR placement. IF5 uses only single bonds, so this mistake is less likely here, yet the rule is worth keeping.

Calling The Shape Octahedral Instead Of Square Pyramidal

Octahedral is the electron geometry for IF5, not the molecular shape. If your question asks “electron geometry,” answer octahedral. If it asks “molecular geometry,” answer square pyramidal.

When you want a trustworthy reference for the identity of IF5 itself (formula, identifiers, structural files), the NIST Chemistry WebBook entry for iodine pentafluoride is a solid stop.

Electron Geometry Practice That Sticks

If IF5 feels easy once you see it, that’s a good sign. Now lock in the method by running the same steps on a few close cousins. This builds pattern recognition without rote memorization.

Run The Same Four Steps On BrF5

Bromine sits above iodine in the same group. BrF5 also ends up with AX5E, so its electron geometry is octahedral and its molecular shape is square pyramidal. You should be able to reach that result by counting electrons and then counting groups.

Contrast With IF7

IF7 has seven I–F bonds and no lone pair on iodine in its standard Lewis picture. That gives steric number 7, which maps to a pentagonal bipyramidal electron geometry. The shift from 6 to 7 groups is the whole story.

Keep A One-Line Memory Hook

If you want a short hook, try this: “Six groups means octahedral; subtract one corner for one lone pair, and you get square pyramidal.” It’s not a shortcut that replaces counting. It’s a check after you count.

IF5 Electron Geometry And Shape Summary Table

The table below compresses the whole decision chain, from electron accounting to the final labels. Use it as a checklist when you practice on paper.

What You Check	IF5 Result	What It Tells You
Central atom	Iodine (I)	Count groups around iodine
Valence electrons	42 total	Build a Lewis structure that fits
Bonding groups	5 I–F bonds	Five regions from bonds
Nonbonding groups	1 lone pair on I	Add one region from the lone pair
Steric number	6	Maps to octahedral electron arrangement
Electron geometry	Octahedral	All six groups placed
Molecular shape	Square pyramidal	Atoms only, lone pair omitted
AXE label	AX5E	Five ligands, one lone pair
Angle expectation	Near 90°	Small shifts near the lone pair

How To Draw IF5 Cleanly In Two Views

Most worksheet points are lost on drawings, not naming. A clean sketch signals that you understand what “electron geometry” is asking for.

View 1: Electron Geometry Sketch

Draw iodine in the center. Place four fluorines in a square around it. Add one fluorine above the square and one lone pair below (or swap). Label the overall arrangement octahedral. This view counts the lone pair as a position.

View 2: Molecular Shape Sketch

Use the same picture, then erase the lone pair. You now see five fluorines: four making a square base, plus one at the top. Label that atom-only picture square pyramidal.

Fast Self-Check

• If you see six “things” around iodine, you are in electron-geometry mode.
• If you see five atoms around iodine, you are in molecular-shape mode.

Test-Day Shortcuts That Stay Honest

You can speed up without guessing by keeping two quick checks in mind.

1. Group count check: If the Lewis structure has 5 bonds and 1 lone pair on iodine, you already know steric number 6.
2. Name check: Steric number 6 always pairs with octahedral electron geometry.

Then write the second label only if the question asks for molecular shape: square pyramidal.

Table Of Shape Patterns Related To IF5

This second table is meant for pattern spotting. Use it when a quiz mixes several interhalogens in one set of questions.

AXE Pattern	Electron Geometry	Molecular Shape
AX5E	Octahedral	Square pyramidal
AX6	Octahedral	Octahedral
AX4E2	Octahedral	Square planar
AX3E3	Octahedral	T-shaped
AX2E4	Octahedral	Linear
AX7	Pentagonal bipyramidal	Pentagonal bipyramidal
AX6E	Pentagonal bipyramidal	Distorted octahedral

One Last Check Before You Submit An Answer

If your prompt says “electron geometry,” your answer for IF5 is octahedral. If it says “molecular geometry” or “molecular shape,” your answer is square pyramidal. If it asks for both, give both in that order.

That’s the full chain: count electron groups around iodine, match steric number 6 to octahedral electron geometry, then remove the lone pair to get a square pyramidal molecular shape.