Chemical Bonding:

No. of electrons in outermost orbit                 Bond Order


20                                                                    0.0

19                                                                    0.5 

18                                                                     1  

17                                                                    1.5

16                                                                     2

15                                                                     2.5

14                                                                     3

13                                                                     2.5

12                                                                     2.0  

11                                                                     1.5

10                                                                     1.0

9                                                                       0.5

8                                                                        0  


Magnetic Property: Remember  "DEPO"

D - Diamagnetic  if Even no of electron
P-Paramagnetic if odd no of electron 

i.e   Dia if Even Para if Odd = = DEPO 


Example:  
One negative charge will add one electron and one positive will subtract one electron.


CN-  , N0+  N0-   CO   CN   CO+  O2+  O2-  

CN-   =   6 + 7 + 1 = 14 ...B.O = 3    and no of electron are even so Diamagnetic in nature 

NO+  = 7 + 8 - 1 =  14  ...B.O = 3   and no of electrons are even(14) so diamagnetic in nature 

NO- = 7 + 8 + 1 = 16    B,O = 2   and again Dia in nature 

CO = 6 + 8 = 14   B.O= 3   again diamagnetic in nature ( 14 e and is even) 

O2+ =  2(8) - 1 = 15  B.O = 2.5    and is paramagnetic in nature ..coz odd no of electron ( 15 is odd) 

O2-  = 2(8) + 1 = 17   B.O = 1.5  and is paramagnetic in nature ..

CO+ =  6 + 8 - 1 = 13  B.O = 2.5 ....and is paramagnetic in nature due to odd no of electrons ( 13 electron) 


EXCEPTION:  O2 and B2 

O2 = 16 electron   and B2 = 10 electron ....both have even no of electron but then also they are PARAMAGNETIC in nature...


Just remember these two exception and apply it for others ..

Solve for :  N2+  N2-   CN NO+  NO-   ....and go through previous year question on B.O .....


All the mentioned compounds have been asked in JEE many times...


Comment ...on this..if u are unable to understand or any question ?