The acidity of $\alpha$-hydrogens (hydrogens attached to the carbon adjacent to a functional group) depends on the stability of the conjugate base formed after proton removal.

1. Ketones: The $\alpha$-hydrogen in carbonyl compounds like ketones is acidic due to two factors:

• Electron-withdrawing effect (-I): The carbonyl group ($>C=O$) pulls electron density, weakening the $C-H$ bond.
• Resonance Stabilization: The conjugate base (enolate ion) is stabilised by resonance, where the negative charge is delocalised onto the electronegative oxygen atom.

2. Comparison: Alkanes, alkenes, and amines generally have much higher $pK_a$ values (lower acidity) because their conjugate bases lack this degree of stabilization. Therefore, a strong base readily abstracts a proton from a ketone compared to the others.