Answer
Verified
457.2k+ views
Hint: $B{F_3}$undergoes back bonding which leads to double bond character, while $B{F_2} - OH$ and $B{F_2} - N{H_2}$have electronegative atoms O and N involved of which O is more electronegative than N.
Complete step by step answer:
> In $B{F_3}$: It has a $s{p^2}$ hybridised structure and so a trigonal planar structure. B has vacant 2p orbital while F atoms have completely filled unutilised 2p orbitals. Since both of these orbitals are of the same energy level (2p), pπ-pπ back bonding occurs between B and F. In this a lone pair of electrons from the unutilised completely filled orbital of F is transported to the vacant 2p orbital of B atom. This type of back bonding causes the bond between B and F to develop a double bond character. This causes the bond length B-F to be shorter than normal.
Hence it has the shortest bond length here.
> In $B{F_4}^ - $: It is $s{p^3}$ hybridised with a tetrahedral shape and B atom here does not have any vacant 2p orbital left and so there is no scope for back bonding. So, all the B-F bond lengths are purely single bonds.
So, they have a higher bond length than $B{F_3}$.
> Now talking about $B{F_2} - OH$ and $B{F_2} - N{H_2}$: we know that electronegativity of O is much more than that of N.
Electronegativity has a direct effect on the bond length between 2 atoms. A more electronegative atom has a higher tendency to pull the pair of electrons forming the bond towards itself. This causes the bond length to become shorter than usual and since O is more electronegative than N, it attracts the bonding electrons more and so the bond length of B-F is shorter in $B{F_2} - OH$as compared to $B{F_2} - N{H_2}$. But still this bond length is more than double bond length but less than that of single bond.
> So the bond length is smallest in $B{F_3}$, followed by $B{F_2} - OH$, then $B{F_2} - N{H_2}$ and that of $B{F_4}^ - $ is the longest.
Hence the correct option is: (A).
Note: Back bonding occurs only if one of the atoms has a vacant orbital and other atom has a lone pair of electrons to transfer. Both of these should involve orbitals of the same energy only.
Also a more electronegative atom attracts the bonding electron pair towards it more and so has a shorter bond length as compared to lesser electronegative atoms.
Complete step by step answer:
> In $B{F_3}$: It has a $s{p^2}$ hybridised structure and so a trigonal planar structure. B has vacant 2p orbital while F atoms have completely filled unutilised 2p orbitals. Since both of these orbitals are of the same energy level (2p), pπ-pπ back bonding occurs between B and F. In this a lone pair of electrons from the unutilised completely filled orbital of F is transported to the vacant 2p orbital of B atom. This type of back bonding causes the bond between B and F to develop a double bond character. This causes the bond length B-F to be shorter than normal.
Hence it has the shortest bond length here.
> In $B{F_4}^ - $: It is $s{p^3}$ hybridised with a tetrahedral shape and B atom here does not have any vacant 2p orbital left and so there is no scope for back bonding. So, all the B-F bond lengths are purely single bonds.
So, they have a higher bond length than $B{F_3}$.
> Now talking about $B{F_2} - OH$ and $B{F_2} - N{H_2}$: we know that electronegativity of O is much more than that of N.
Electronegativity has a direct effect on the bond length between 2 atoms. A more electronegative atom has a higher tendency to pull the pair of electrons forming the bond towards itself. This causes the bond length to become shorter than usual and since O is more electronegative than N, it attracts the bonding electrons more and so the bond length of B-F is shorter in $B{F_2} - OH$as compared to $B{F_2} - N{H_2}$. But still this bond length is more than double bond length but less than that of single bond.
> So the bond length is smallest in $B{F_3}$, followed by $B{F_2} - OH$, then $B{F_2} - N{H_2}$ and that of $B{F_4}^ - $ is the longest.
Hence the correct option is: (A).
Note: Back bonding occurs only if one of the atoms has a vacant orbital and other atom has a lone pair of electrons to transfer. Both of these should involve orbitals of the same energy only.
Also a more electronegative atom attracts the bonding electron pair towards it more and so has a shorter bond length as compared to lesser electronegative atoms.
Recently Updated Pages
what is the correct chronological order of the following class 10 social science CBSE
Which of the following was not the actual cause for class 10 social science CBSE
Which of the following statements is not correct A class 10 social science CBSE
Which of the following leaders was not present in the class 10 social science CBSE
Garampani Sanctuary is located at A Diphu Assam B Gangtok class 10 social science CBSE
Which one of the following places is not covered by class 10 social science CBSE
Trending doubts
Which are the Top 10 Largest Countries of the World?
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
Give 10 examples for herbs , shrubs , climbers , creepers
The Equation xxx + 2 is Satisfied when x is Equal to Class 10 Maths
How do you graph the function fx 4x class 9 maths CBSE
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
Change the following sentences into negative and interrogative class 10 english CBSE
Why is there a time difference of about 5 hours between class 10 social science CBSE
Differentiate between homogeneous and heterogeneous class 12 chemistry CBSE