Molecular Shape of Covalent Compound

1. Molecules and Molecular Structure Molecular Shape of Covalent Compound Sharifah Mona Abdul Aziz Abdullah Abdul Al-Hafiz Ismail Centre for Pre-University Studies Universiti Malaysia Sarawak This OpenCourseWare@UNIMAS and its related course materials are licensed under a Creative Commons Attribution- NonCommercial - ShareAlike 4.0 International License.

2. Basic molecular shape There are five basic molecular shape where the central atom has bonding pair electrons only: 1) Linear 2) Trigonal planar 3) Tetrahedral 4) Trigonal bipyramidal 5) Octahedral

3. Basic molecular shape Name Bonding pairs Shape Linear 2 Trigonal planar 3 Tetrahedral 4 F F Be F F F B H H H C H

4. Name Bonding pairs Shape Trigonal bipyramidal 5 Octahedral 6 Cl Cl Cl P Cl Cl Basic molecular shape F F F P F F F

5. Effect of lone pair electrons on the molecular shape and bond angle Bonding pair electrons occupy less spatial distribution than lone pair because the electrons are strongly attracted by the nucleus of the two bonded atoms. On the other hand, lone pair electrons occupy more space than bonding pairs because they experience greater repulsion from neighbouring lone pairs and bonding pairs.

6. The molecules below have 3 electron pairs surrounding the central atom. F F F B H O H C Boron triflouride 3 bond pairs , 0 lone pair Molecular Shape: Trigonal planar Bond angle: 120° Methanal * 3 bond pairs , 0 lone pair Molecular Shape: Trigonal planar Bond angle: 120° Sulphur dioxide 2 bond pairs , 1 lone pair Molecular shape: Bent / V-shape Bond angle: 120° O O S Effect of lone pair electrons on the molecular shape and bond angle

7. The molecules below have 4 electron pairs surrounding the central atom. H H H C H H H N H H H O Methane 4 bond pairs , 0 lone pair Molecular shape: Tetrahedral Bond angle: 109.5° Ammonia 3 bond pairs, 1 lone pair Molecular shape: Trigonal pyramidal Bond angle: 107° Water 2 bond pairs, 2 lone pairs Molecular shape: Bent / V-shape Bond angle: 104.5° Effect of lone pair electrons on the molecular shape and bond angle

8. The molecules below have 5 electron pairs surrounding the central atom. Cl Cl Cl P Cl Cl F F F S F F F Cl F F Xe F Phosphorus (v) chloride 5 bond pairs , 0 lone pair Molecular shape: Trigonal bipyramidal Bond angle: 90° and 120° Sulphur tetrafluoride 4 bond pairs , 1 lone pair Molecular shape: See-saw Bond angle: <90° Chlorine trifluoride 3 bond pairs , 2 lone pairs Molecular shape: T-shape Bond angle: <90° Xenon Difluoride 2 bond pairs, 3 lone pairs Molecular shape: Linear Bond angle: 180° Effect of lone pair electrons on the molecular shape and bond angle

9. Effect of lone pair electrons on the molecular shape and bond angle The molecules below have 6 electron pairs surrounding the central atom. F F F P F F F F F F Br F F Sulphur hexafluoride 6 bond pairs , 0 lone pair Molecular shape: Octahedral Bond angle:90° Bromine pentafluoride 5 bond pairs , 1 lone pair Molecular shape: Square pyramidal Bond angle:90° and 180° Xenon tetrafluoride 4 bond pairs , 2 lone pairs Molecular shape: Square planar Bond angle: 90° F F F F Xe

10. # electron pair Electron pair orientation # bond pair # lone pair Molecular shape 2 Linear 2 Linear 3 Trigonal planar 3 Trigonal planar 2 1 Bent / V-shape 4 Tetrahedral 4 Tetrahedral 3 1 Trigonal pyramidal 2 2 Bent / V-shape 5 Trigonal bipyramidal 5 Trigonal bipyramidal 4 1 See-saw 3 2 T-shape 2 3 Linear 6 Octahedral 6 Octahedral 5 1 Square pyramidal 4 2 Square planar Summary of Molecular Geometry