In the series of group 5A hydrides, of general formula MH3, the measured bond distances are P—H. 1.419 A; As—H. 1.519 A; Sb—H. 1.707 A. (a) Compare these values with those estimated by use of the atomic radii in Figure, (b) Explain the steady increase in M—H bond distance in this series in terms of the electron configurations of the M atoms. A Figure Trends in bonding atomic radii for periods 1 through 5. Which part of the periodic table (top/bottom. left/right) has the elements with the largest atoms?
Solution Step 1 (a)The M-H bond distance can be compared with the help of a table Bond Measured value Calculated value (using atomic radii (from question) measurements) P-H 1.419 Atomic radius of P+atomic radius of H =(1.07+.0.31)A =1.38A° ° As-H 1.519 Atomic radius of P+atomic radius of H ° ° =(1.19+.0.31)A =1.50A Sb-H 1.707 Atomic radius of P+atomic radius of H =(1.39+.0.31)A =1.70A° ° The values calculated using atomic radius is lower.