How does nickel tetracarbonyl satisfy the 18-electron rule?

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periodic table with group numbers and the s, p, d, and f blocks — organometallic compound The periodic table of the elements, displaying the group numbers and the s, p, d, and f blocks. Elements in the shaded area are the metals of organometallic chemistry.

Nickel tetracarbonyl, ${Ni(CO)}_{4}$ , satisfies the 18-electron rule by achieving a stable valence shell configuration through the combination of electrons from the central metal atom and its ligands.1

The electron count is calculated as follows:
* Nickel atom: As a neutral atom, nickel provides 10 valence electrons.1
* Carbonyl ligands: Each of the four carbon monoxide (CO) ligands contributes two electrons to the metal center.21

Summing these contributions:
$10 (from Ni) + 4 \times 2 (from CO) = 18 electrons$

This total of 18 electrons provides the complex with a stable electronic structure, often compared to the configuration of noble-gas atoms, which contributes to the stability of the organometallic compound.1