Which of the following elements is most metallic?

How do you account for the reducing behaviour of $H_{3}PO_{2}$ on the basis of its structure?

When orthophosphoric acid is heated to $600\,^oC$,it forms .................. .

The correct order of reducing abilities of hydrides of $V$ group elements is

Which of the following ions does not exist in an aqueous solution?

The orange solid on heating gives a colourless gas and a green solid which can be reduced to metal by aluminium powder. The orange and the green solids are,respectively