Which of the following is wrong statement
(A) $Ni{{(CO)}_{4}}$ has oxidation number of +4 for Ni
(B) $Ni{{(CO)}_{4}}$ has oxidation number of 0 for Ni
(C) Ni is metal
(D) CO is gas

Hint: To proceed in this question, we’ll look at one option at one time. First, we will see the oxidation number of Ni in $Ni{{(CO)}_{4}}$ and then we’ll look at the properties of Ni and CO. For, oxidation number, let's suppose the oxidation state of Ni to be x. We must first add the oxidation states of the remaining elements until the total is equal to the net charge in the molecule.

Complete Step by Step Solution:
If we look at the first two options then we can see that they are related to the oxidation number of Nickel in the compound$Ni{{(CO)}_{4}}$. So, we’ll start with finding the oxidation number of Ni.

We first must know that the given compound is a coordination compound in which the $CO$ molecule is acting as a ligand.
The term "oxidation number" refers to the fictitious charge that an atom would possess if all of its connections to other atoms were fully ionic in character.

To proceed further let’s suppose the oxidation number of Ni to be x.
So, we can see that the complex has a net charge of 0 and we know that $CO$ is a neutral ligand and thus has a charge of 0.
So, oxidation state of Ni can be given as
$x+4(0)=0$ Where, x is the oxidation state of Ni

After solving it we get $x=0$ and hence, the oxidation state of Nickel in the given compound is$0$.
Therefore, for the first two options we can see that option A is an incorrect statement and option B is a correct statement.

The chemical element nickel has the atomic number 28 and the symbol Ni. It is a shiny, silvery-white metal with a little hint of gold. A transition metal with ductility and hardness is nickel. However, larger pieces are slow to react with air under ordinary conditions because an oxide layer builds on the surface and stops further corrosion. Pure nickel, powdered to increase reactive surface area (passivation). So, Ni is a metal.

Colourless, extremely deadly, odourless, tasteless, and combustible gas with the molecular formula CO, carbon monoxide is somewhat less dense than air. One carbon atom and one oxygen atom bound together by three bonds make up carbon monoxide. The oxocarbon family's simplest molecule is this one. The carbon monoxide ligand in coordination complexes is referred to as carbonyl.
Therefore, the correct option is A. $Ni{{(CO)}_{4}}$ has an oxidation number of +4 for Ni.

Note: In these types of questions, you need to read the options carefully. In this question you need to know the concept of oxidation number and the way to calculate the oxidation numbers of complexes. After that, you need to memorise the properties of Ni and CO.