Why is hydrogen regarded as a unique element?

Why is zinc not regarded as a transition element ? (At. No. Zn = 30)

(i) Name the element of 3d transition series which shows maximum number of oxidation states. Why does it show so ? (ii) Out of Cr_(3+) and Mn^(3+) which is a stronger oxidising agent and why? (iii) Why is zinc not regarded as a transition element ? (At. no. Zn=3)

Scandium forms no coloured ions, yet it is regarded as a transition elements. Explain why?

Why is hydrogen peroxide used as a bleaching agent ?

Why is pure water regarded as a weak electrolyte ?

Why is ionic bond regarded as an extreme case of a polar covalent bond?

Why is green chemistry regarded as an alternative tool for reducing pollution ?

What are the characteristics of th transition elements and why are they called transition elements? Which of the d-block elements may not be regarded as the transition elements?

Why is H_2O regarded a Lewis base?

Why does hydrogen show dual nature ?