NCERT Class XI Chemistry Solutions
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Question : 40
Total: 40
What is meant by the term bond order?
Calculate the bond order of :N 2 , O 2 , O 2 + O 2 –
Calculate the bond order of :
Solution:
Bond order of a molecule or an ion is a measure of the strength or stability of the bond. Numerically, it is half of the difference between number of electrons in bonding ( N b ) ( N a )
Bond order =
( N b − N a ) .
If B.O. is zero or negative, the bond is highly unstable, i.e. the molecule does not exist. Higher bond order means high bond dissociation energy and greater stability. Greater the bond order, lesser is the bond length.
M.O. configuration ofN 2
K K σ ( 2 s ) 2 σ * ( 2 s ) 2 π ( 2 p x ) 2 π ( 2 p y ) 2 σ ( 2 p z ) 2
Bond order =
( 8 − 2 )
Thus, nitrogen molecule has three bonds, one sigma and two pi. The molecule is diamagnetic.
M.O. configuration of O2 :
K K σ ( 2 s ) 2 σ * ( 2 s ) 2 σ ( 2 p z ) 2 π ( 2 p x ) 2 π ( 2 p y ) 2 π * ( 2 p x ) 1 π * ( 2 p y ) 1
[Note :σ ( 2 p z ) π ( 2 p x ) π ( 2 p y )
Bond order =
The oxygen molecule has two bonds (one sigma and one pi). The molecule is paramagnetic.
M.O. configuration ofO 2 +
K K σ ( 2 s ) 2 σ * ( 2 s ) 2 σ ( 2 p z ) 2 π ( 2 p x ) 2 π ( 2 p y ) 2 π * ( 2 p x ) 1
Bond order =
M.O. configuration ofO 2 –
K K σ ( 2 s ) 2 σ * ( 2 s ) 2 σ ( 2 p z ) 2 π ( 2 p x ) 2 π ( 2 p y ) 2 π * ( 2 p x ) 2 π * ( 2 p y ) 1
Bond order =
Bond order =
If B.O. is zero or negative, the bond is highly unstable, i.e. the molecule does not exist. Higher bond order means high bond dissociation energy and greater stability. Greater the bond order, lesser is the bond length.
M.O. configuration of
Bond order =
Thus, nitrogen molecule has three bonds, one sigma and two pi. The molecule is diamagnetic.
M.O. configuration of O2 :
[Note :
Bond order =
The oxygen molecule has two bonds (one sigma and one pi). The molecule is paramagnetic.
M.O. configuration of
Bond order =
M.O. configuration of
Bond order =
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