The number of geometrical isomers possible in triamminetrinitrocobalt (III) is X and in trioxalatochromate (III) is Y. Then the value of X + Y is _______________.

Three moles of AgCl get precipitated when one mole of an octahedral co-ordination compound with empirical formula CrCl₃.3NH₃.3H₂O reacts with excess of silver nitrate. The number of chloride ions satisfying the secondary valency of the metal ion is ______________.

The total number of unpaired electrons present in [Co(NH₃)₆]Cl₂ and [Co(NH₃)₆]Cl₃ is :

An aqueous solution of NiCl₂ was heated with excess sodium cyanide in presence of strong oxidizing agent to form [Ni(CN)₆]^2$$-$$. The total change in number of unpaired electrons on metal centre is _______________.