Bond parameter- Bond length, bond angle and bond energy

 Bond parameter-

 Bond Length-

 The average distance between the nucleus of two atoms is known as bond length, normally it is represented in Å or pm  

Factors Affecting Bond Length

(a) electronegativity: - Bond length proportional to EN

                                             Therefore               H—F < H—Cl < H—Br < H—I

(b) Bond order or number of bonds: - Bond length α 1/Number of bonds or bond order

                                                                     ex.        C—C,      >      C = C  >    C = C

                                                 bond length          154pm             134pm      120pm

Bond Angle- The minimum angle between any two adjacent bonds is known as bond angle. It is represented in degree (°), min (') and second (")

Factors affecting the bond angle –

a). Hybridization— bond angle is proportional to  % 's' character

                                   BeCl2     > BCl3           > CCl4

          bond Angle      180°          120°          109.28'

Hybridizations-           sp               sp2              sp3

% s- character            50%           33.33%       25%

b). Lone pair —When hybridization is same, lone pair are different

      Bond angle is inversely proportional to No. of lone pair Example-

                               CH₄                        NH₃                     H₂O

Hybridization     sp³                      sp³                       sp³

Bond angle        109.28'                107°                     104.5°         

No of lone pair    0                       1                            2

c) nature of Central Atom

                 Bond angle is proportional to the Electronegativity of central atom

Example -

                       NH3         >       PH3       > AsH3

 Bond angle  107°                   93°            91°  

 - Electronegativity decreases from N to As , so,  Bond angle will decrease

d). Nature of Side atom bonded to a central atom

       Bond angle is proportional to size of the side atom  but is inversely proportional to electronegativity of bonded atom

  Example-

    PF₃ < PCl₃ < PBr₃ < PI₃   ---->   Reason - (Electronegativity of side atom decrease)

    OF₂ < Cl₂O < Br₂O ---->   Reason - (Electronegativity of side atom decrease)

     SF₂ < SCl₂ < SBr₂ ---->   Reason - (Electronegativity of side atom decrease