selenium tetrafluoride, SeF4
valence electrons: Lewis structure: tribromide ion, Brs
valence electrons: dre (indi Geometry description: Hybridization of central atom; Bonding description: Geometry description: Hybridization of central atom; Bonding description
Draw the molecule with the correct shape.
The Correct Answer and Explanation is:
Let’s analyze selenium tetrafluoride (SeF₄) and tribromide ion (Br₃⁻) in terms of:
- Valence electrons
- Lewis structure
- Electron geometry
- Molecular geometry
- Hybridization
- Bonding description
1. Selenium Tetrafluoride (SeF₄)
Valence Electrons:
- Selenium (Se) has 6 valence electrons.
- Each fluorine (F) has 7 valence electrons.
- Total = 6 (Se) + 4×7 (F) = 34 valence electrons
Lewis Structure:
- Se is the central atom.
- Place single bonds between Se and four F atoms.
- Each bond uses 2 electrons × 4 = 8 electrons.
- Remaining: 34 – 8 = 26 electrons → distributed as lone pairs on F and Se.
- Each F gets 6 electrons as lone pairs (24 total for 4 F atoms).
- Remaining 2 electrons are placed as a lone pair on Se.
Electron Geometry:
- There are 5 electron regions (4 bonding pairs, 1 lone pair) around Se.
- Geometry: Trigonal bipyramidal (based on VSEPR)
Molecular Geometry:
- With one lone pair, actual shape is see-saw.
Hybridization:
- 5 electron regions = sp³d
Bonding Description:
- Se forms 4 sigma bonds with F atoms using sp³d hybrid orbitals.
- One lone pair resides in the equatorial position to minimize repulsion.
2. Tribromide Ion (Br₃⁻)
Valence Electrons:
- Each Br has 7 valence electrons → 3×7 = 21
- Add 1 for the negative charge → 22 valence electrons
Lewis Structure:
- Linear arrangement: Br–Br–Br⁻
- The central Br forms two single bonds with the outer Br atoms.
- Lone pairs complete octets; central Br has 3 lone pairs, outer Br atoms each have 3.
Electron Geometry:
- 5 electron domains on central Br (2 bonding, 3 lone pairs) = trigonal bipyramidal
Molecular Geometry:
- With 3 lone pairs, the shape is linear.
Hybridization:
- 5 regions = sp³d
Bonding Description:
- The central Br uses sp³d orbitals to form sigma bonds.
- The linear shape minimizes repulsion from the lone pairs in equatorial positions.
Summary Table
| Molecule/Ion | Valence e⁻ | Electron Geometry | Molecular Geometry | Hybridization | Shape Description |
|---|---|---|---|---|---|
| SeF₄ | 34 | Trigonal bipyramidal | See-saw | sp³d | Four bonds + 1 lone pair |
| Br₃⁻ | 22 | Trigonal bipyramidal | Linear | sp³d | Two bonds + 3 lone pairs |