Determine the molecular geometry of BrF5.
seesaw
trigonal bipyramidal
square pyramidal
octahedral
The correct answer and explanation is :
The correct molecular geometry of BrF₅ (Bromine Pentafluoride) is square pyramidal.
Explanation (300 words)
1. Determining Electron Geometry Using VSEPR Theory
The molecular geometry of BrF₅ can be determined using the Valence Shell Electron Pair Repulsion (VSEPR) theory, which helps predict molecular shapes based on electron pair repulsions.
- Step 1: Count the Valence Electrons of Bromine
Bromine (Br) belongs to Group 17 in the periodic table, so it has 7 valence electrons. - Step 2: Count the Valence Electrons from Fluorine Atoms
Each fluorine (F) contributes 1 valence electron, and since there are five fluorine atoms, the total electrons from fluorine are 5 × 1 = 5 electrons. - Step 3: Determine the Total Valence Electrons
- Br = 7 electrons
- F₅ = 5 × 1 = 5 electrons
- Total = 7 + 5 = 12 electrons (6 electron pairs)
2. Predicting the Electron Pair Arrangement
- The central Br atom has six electron pairs (five bonding pairs from Br–F bonds and one lone pair).
- The electron geometry is based on six electron pairs, which corresponds to an octahedral arrangement.
3. Determining the Molecular Geometry
- Since one of the six electron pairs is a lone pair, the molecular geometry deviates from the octahedral shape.
- The lone pair repels the bonded atoms, distorting the shape into a square pyramidal geometry.
4. Confirming Square Pyramidal Shape
- In square pyramidal geometry, five fluorine atoms form a square base, and the lone pair is positioned at the axial position.
- The bond angles are slightly less than 90° due to lone pair repulsion.