NaOH behaves as a base while Zn(OH)2 is amphoteric why ?

Q: NaOH behaves as a base while Zn(OH)2 is amphoteric why ?

Sol: In NaOH the bond electronegativity difference between Na and oxygen is greater than between H and O and therefore it is the Na–O bond that breaks releasing OH. But in case of Zn—O—H bond the difference of electronegativity of Zn—O and O—H are almost same. So there is equal probability that the bond breaks in both ways leading to an amphoteric behaviour