Among the following, the number of elements showing only one non-zero oxidation state is :
O, Cl, F, N, P, Sn, Tl, Na, Ti

Assuming that Hund’s rule is violated, the bond order and magnetic nature of the diatomic molecule B₂ is

The species having pyramidal shape is

The total number of diprotic acids among the following is:

H₃PO₄, H₂SO₄, H₃PO₃, H₂CO₃, H₂S₂O₇, H₃BO₃, H₃PO₂, H₂CrO₄ and H₂SO₃