Question

what is the valency of Ni in [Ni(CO)4]​

Answer 1

iNickel carbonyl (IUPAC name: tetracarbonylnickel) is the organonickel compound with the formula Ni(CO)4. This colorless liquid is the principal carbonyl of nickel. It is an intermediate in the Mond process for producing very high-purity nickel and a reagent in organometallic chemistry, although the Mond Process has fallen out of common usage due to the health hazards in working with the compound. Nickel carbonyl is one of the most dangerous substances yet encountered in nickel chemistry due to its very high toxicity, compounded with high volatility and rapid skin absorption.[3]

Answer 2

Explanation:

Ionizable valency is the one which is associated with the net charge on complex sphere and since in this case it is zero so it has no ionizable valency.