may i say that nucleophiles donate electrons so they show +I effect ?? do elements having their octet complete donate electrons ?? in which group (+I,-I) we can classify them ??

please answer all very fast .. and in a little deep if possible so that i can understand

Don't compare the nucleophilic ability with inductive effect. 

Inductive effect is an electronic effect due to the polarisation of σ bonds within a molecule or ion. This is typically due to an electronegativity difference between the atoms at either end of the bond.  There are two types of inductive effect: +I and –I effect. Atoms or groups which pull electron density towards themselves are considered as exhibiting negative Inductive effect (–I) and groups which push electron density away from themselves exhibit positive Inductive effect (+I). 

.Example:

Negative inductive effect (-I) is shown by groups which withdraw electrons.The order of (-I) effect of the groups is as follows:

Look care fully that all the species mentioned above have strong tendency to pull electron towards itself.
 

Positive inductive effect (+I) is shown by groups which donate electrons.The order of (+I) effect of the groups is as follows: