Ch.10 - Molecular Shapes & Valence Bond TheoryWorksheetSee all chapters
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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

Solution: The bond angles increase steadily in the series PF3, PCl3, PBr3 and PI3. After consulting the data on atomic radii in Chapter 8 in the textbook, provide an explanation for this observation.

Solution: The bond angles increase steadily in the series PF3, PCl3, PBr3 and PI3. After consulting the data on atomic radii in Chapter 8 in the textbook, provide an explanation for this observation.

Problem

The bond angles increase steadily in the series PF3, PCl3, PBr3 and PI3. After consulting the data on atomic radii in Chapter 8 in the textbook, provide an explanation for this observation.

Solution
  • PF3, PCl3, PBr3 and PIwill appear to have the same geometry since F, Cl, Br and I are in the same group (column). They will appear to have the same number of valence electrons
  • P will appear to have 5 while F, Cl, Br and I have 7 valence electrons. Total valence electrons for each molecule is 26 (5(1) + 7(3) = 26). 
  • P will be the central atom (less electronegative) while being single bonded to each halogens (X). P will have a lone pair in this case while halogen atom has 3. 
  • Formula appears to be AX3E1 where A is the central atom, X is the atoms and E is the lone pairs attached, this particular structure follows a trigonal pyramidal geometry.
  • Since it has 4 groups on it, it is expected to follow a bond angle of 109.5° (bond angles of tetrahedral structure) however it deviates due to the presence of lone pairs. Expected bond angles will appear as < 109.5° due to the lone pair repelling other groups.
  • General structure of the molecules as PX3 (X = halogen) will appear as:
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