Which complexes have zero oxidation state?

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

$A$ coordination complex compound of cobalt has a molecular formula containing five ammonia molecules,one nitro group,and two chlorine atoms for one cobalt atom. One mole of this compound produces three moles of ions in an aqueous solution,and upon reacting with an excess of $AgNO_3$,it forms $AgCl$ precipitate. The ionic formula for this complex would be:

What is the coordination number of the central metal ion in $[Fe(C_2O_4)_3]^{3-}$?

Which of the following ligands forms a chelate?

Which of the following coordination complexes contains a neutral ligand?