Ch.9 - Bonding & Molecular StructureWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Sections
Chemical Bonds
Lattice Energy
Lattice Energy Application
Born Haber Cycle
Dipole Moment
Lewis Dot Structure
Octet Rule
Formal Charge
Resonance Structures
Additional Practice
Bond Energy

Solution:  For the molecule BF3, if we write the Lewis dot structure by first completing the octet around the pendant F atoms, we find that we have used all the valence electrons but the B has less than an octe

Problem

 For the molecule BF3, if we write the Lewis dot structure by first completing the octet around the pendant F atoms, we find that we have used all the valence electrons but the B has less than an octet (Structure A). Using our rules for drawing Lewis dot structures, we complete the octet around the B by forming double bonds from one of the F atoms which give rise to the resonance structures shown in Structure B. Structural characterization of BF3 suggests that there are no double bonds to F and that Structure A is the actual structure even though is does not obey the octet rule. In this case we can justify this structure based on Formal Charge arguments. Determine the formal charge on all the atoms in the electron deficient structure, Structure A, and on one of the resonance structures in Structure B and, using the rules of Formal Charge, tell why Structure A is the preferred one.