Nucleophile- electron pair donor. If electron dense it's therefore attracted to a positive charge. A partial positive charge can be found on the C atom due to the electronegativity of chlorine. Therefore, CN-, NH3- attack the centre and undergo a substitution reaction. (Draw Mechanism)Product with NH3: CH3CH2NH2 aminoethane/ethylamine.Can undergo further substitution due to lone pair of electrons on the amine also acting as a nucleophile, all the way to a quaternary ammonium salt unless there's an excess of ammonia.