CH3NH2, also known as methylamine, is classified as a Lewis base. A Lewis base is defined as a substance that can donate an electron pair to form a covalent bond. In the case of methylamine, it contains a nitrogen atom that has a lone pair of electrons. This lone pair can be donated to a Lewis acid, which is an electron pair acceptor.
Methylamine can easily donate its lone pair of electrons due to the presence of the nitrogen atom, which is less electronegative than carbon. This property allows CH3NH2 to act as a nucleophile in chemical reactions, meaning it can react with Lewis acids by donating its electrons.
In summary, because methylamine has a lone pair of electrons available for donation, it is classified as a Lewis base rather than a Lewis acid.