The correct IUPAC name of [Ni(CO)4] is:

🧠 Zero Counts as a Number

Tetracarbonyl nickel is the textbook neutral metal-carbonyl. Two things make it a frequent JEE option-trap:

1. The metal oxidation state is 0, and in IUPAC names you must write that 0 explicitly: "nickel**(0)**".
2. The complex is neutral, not anionic — so the metal name stays "nickel", not "nickelate".

🗺️ Build the Name

Ligand block. 4 × carbonyl → "tetracarbonyl". (CO is treated as a simple ligand → "tetra-", not "tetrakis-".)

Oxidation state. $\mathrm{Ni}$ has zero charge; $\mathrm{CO}$ is neutral; the entire complex is neutral. So $\mathrm{Ni}$ is in oxidation state 0.

Metal block. Neutral complex → "nickel", with (0) appended.

Stitched: tetracarbonylnickel(0) — option (2).

⚡ The "(0) Always Stated" Rule

Even when the metal's oxidation state is zero, IUPAC requires the Roman-numeral parenthesis. Options that drop the (0) — like option (4) "Tetracarbonylnickel" — are wrong on a technicality but a deliberate one.

⚠️ Common Name vs IUPAC

"Nickel tetracarbonyl" (option 1) is the traditional name still used in industry. IUPAC convention puts the ligand block first, then the metal — so "tetracarbonylnickel(0)" is correct, "nickel tetracarbonyl" is not. Likewise, "tetracarbonylnickelate(0)" (option 3) is wrong because the complex is neutral, not anionic.

$\boxed{\text{Answer: (2) Tetracarbonylnickel(0)}}$