Which of the following is a negatively charged bidentate ligand?

The coordination number of $Cu$ in $[Cu(H_2O)_4]^{2+}$ is ...... .

Consider the following statements according to Werner's theory:
$1.$ Ligands are connected to the central metal ions by coordinate bonds.
$2.$ Secondary valencies have directional properties.
$3.$ Secondary valencies are non-ionisable.
Which of these statements are correct?

The oxidation number of iron in the compound formed during the brown ring test for $NO_3^{-}$ ion is . . . . . .

Give the chemical formulas for the following compounds:
$(i)$ Ammonium molybdate
$(ii)$ Ammonium phosphomolybdate
$(iii)$ Ferric thiocyanate ion
$(iv)$ Sodium sulphide

The oxidation state and covalency of $Al$ in $[AlCl(H_2O)_5]^{2+}$ respectively are