BASICITY ORDER AMONG ETHYL AMINE , PHENYL AMIDE AND METHYL AMIDE

The acid/base process you're looking at in this question is the dissociation of a proton from the NH2 to form NH- (acid) or the acceptance of a proton by the NH2 to form NH3+ (base). So anything that stabilizes a negative charge on the nitrogen increases acidity, but also destabilizes the positive charge so it decreases basicity. Negative charge is stabilized by the carbonyl in acetamide more than in ethyl amine. The carbonyl, with its double bond and the electronegative oxygen, help to delocalize and stabilize the negative charge.

Resonance: Resonance is a stabilizing feature. If resonance is lost upon sharing the
nitrogen lone pair, then this resonance decreases the nucleophilicity and basicity of
the amine. The point is illustrated with aniline (PhNH2).

so phnh2>ch3ch2nh2>ch3conh2

phenyl amide>ethyamine>methyl emide