What are the factors that affect the basicity of amines?

There are several factors which affect the basicity of amines. 

• One factor is as the negative charge on nitrogen increases, the basicity of the amine rises. 
• Another factor is electron-withdrawing groups nearby reduce the basicity of amines through inductive effects. Additionally, conjugated amines are less basic compared to non-conjugated amines. 
• Aromatic amines are typically less basic compared to their aliphatic counterparts. This is because the lone pair of electrons on the nitrogen atom is delocalized into the aromatic ring. 
• The hybridization of the nitrogen atom in an amine also affects its basicity. The greater the s-character in the hybrid orbital of the nitrogen atom, the more electronegative it is and thus the more stable the lone pair. This results in decreased basicity. The basicity of nitrogen peaks with the sp3-hybridized nitrogen.