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.

FREE Expert 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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Problem Details

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.

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