[orgoclear]

Does this nitrogen show chirality :NABC (eg. :NH(CH3)(C2H5) where A,B,C are three different substituents?

I think it does because the lone pair can show a directional "bond" sort-of behaviour that enables it to have chiral behaviour. But ive found that in some places it has chirality while in some other places it does not.

[sjb]

Have a look at things like http://en.wikipedia.org/w/index.php?title=Nitrogen_inversion&oldid=247366848 or similar

[Enantiomer]

While you can't describe this molecule as chiral it does have molecular symmetry (as do all molecules really even if it's just C₁), if you ever divulge into inorganic chemistry the symmetry of all compounds will become slightly clearer.