Borax is treated with hot conc .HCl to get NACl and compound A .The oxidation state of B in compound A is

The compound with the lowest oxidation state is:

Elements of group-15 form compounds in +5 oxidation state. However, bismuth forms only one well characterised compound in +5 oxidation state. The compound is :

Elements of group - 15 compounds in +5 oxidation state. However, bismuth forms only one well characterised compound in +5 oxidation state. The compound is

Hot and concentrated solution of Borax is treated with HCl to give A and B . B on strong heating undergoes dehydration to give C .Then C is.

Which of the transition metal forms green compound in its +3 oxidation state and yellow to orange compound in +6 oxidation state?