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Chemistry Question 53 – JEE-MAIN 2026

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Bromine trifluoride autoionizes to form BrF2⊕ and BrF4⊖. The shapes of the cation and anion are respectively _______ and _______.

The Valence Shell Electron Pair Repulsion (VSEPR) theory is used to predict the geometry of individual molecules or ions from the number of electron pairs surrounding their central atoms.

Step 1: Determine the shape of BrF2⊕✦ Active

For BrF2⊕:

Central atom: Br. Valence electrons = 7.

Electrons from 2 F atoms (single bonds) = 2.

Charge = +1, so subtract 1 electron.

Total valence electrons = 7+2−1=8 electrons.

Number of electron pairs = 8/2=4 electron pairs.

Number of bonding pairs = 2 (Br-F bonds).

Number of lone pairs = 4−2=2 lone pairs.

Steric number = 2 (bonding pairs)+2 (lone pairs)=4.

Electron geometry: Tetrahedral. Molecular geometry: **Bent**.

Step 2: Determine the shape of BrF4⊖○ Expand

For BrF4⊖:

Central atom: Br. Valence electrons = 7.

Electrons from 4 F atoms (single bonds) = 4.

Charge = -1, so add 1 electron.

Total valence electrons = 7+4+1=12 electrons.

Number of electron pairs = 12/2=6 electron pairs.

Number of bonding pairs = 4 (Br-F bonds).

Number of lone pairs = 6−4=2 lone pairs.

Steric number = 4 (bonding pairs)+2 (lone pairs)=6.

Electron geometry: Octahedral. Molecular geometry: **Square planar**.

Step 3: Match the shapes with the options○ Expand

The shapes of the cation (BrF2⊕) and anion (BrF4⊖) are bent and square planar, respectively. This corresponds to option 1.

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