Question

The correct order of bond angles in $BF _{3}, NH _{3}, NF _{3}$ and $PH _{3}$ is

• A. $BF _{3}> NH _{3}> NF _{3}> PH _{3}$
• B. $PH _{3}> BF _{3}> NF _{3}> NH _{3}$
• C. $BF _{3}> PH _{3}> NH _{3}> NF _{3}$
• D. $NH _{3}> NF _{3}> BF _{3}> PH _{3}$

Answer 1

Answer: (A)

$ BF_3$ is trigonal planar hence,



The bond angle decrease, if the electronegativity of the surrounding atom increase (VSEPR theory).



If the electronegativity of central atom decrease, bond angle decrease (VSEPR theory).

$NH _{3}> PH _{3}$

The correct order is

$BF _{3}\left(120^{\circ}\right)> NH _{3}\left(107^{\circ}\right)> NF _{3}\left(102^{\circ}\right)> PH _{3}\left(94^{\circ}\right)$