Nickel (Ni) is a transition metal with atomic number 28. Its electron configuration is important for understanding its chemistry, oxidation states, and coordination compounds.
Unlike Cu (Z=29) and Cr (Z=24) which have anomalous configurations due to extra stability of half-filled/fully-filled d orbitals, Ni follows the regular aufbau configuration with [Ar] 3d⁸ 4s².
Atomic Number (Z): 28
Full Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s²
Noble Gas (Short) Notation: [Ar] 3d⁸ 4s²
Where [Ar] = 1s² 2s² 2p⁶ 3s² 3p⁶ (18 electrons of Argon)
The 3d subshell of Ni has 8 electrons arranged as:
Ni most commonly shows +2 oxidation state (Ni²⁺):
Ni²⁺ configuration: [Ar] 3d⁸ (loses 4s electrons first)
Ni also shows 0 (in carbonyls like Ni(CO)₄) and +3, +4 oxidation states.
Ni has **2 unpaired electrons** in its 3d subshell (3d⁸ has two singly occupied orbitals by Hund's rule), making it paramagnetic.
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