Why 3 d - series of elements acts as good catalyst?

Why 3d-series of elements acts as good catalyst?

In stratosphere , which of the following element acts as a catalyst in degradation of ozone an release of molecular oxygen ?

Which series of elements should have nearly the same atomic radii?

The thermonuclear reaction of hydrogen inside the stars is taking place by a cycle of operations. The particular element which acts as catalyst is

Which one of the following also acts as a catalyst in a bacterial cell ?

State reasons for the following: (i) Cu(I) ion is not stable in an aqueous solution. (ii) Unlike Cr^(3+)Mn^(2+), Fe^(3+) and the subsequent other M2+ ions of the 3d series of elements, the 4d and the 5d series metals generally do not form stable cationic species.

Name one 3d series element that do not show variable oxidation state.

Why are transition elements so named ?