Q.Calculate the Effective Atomic Number (EAN) of the central metal in

[!TLDR] Both reach 36 (krypton) — Co(III), CN=6; Ni(0), CN=4. [!ANSWER] (a) $\text{EAN}(\text{Co}) = 27-3+1 …

(a) In $[\text{Co}(\text{NH}_3)_6]^{3+}$, the six \text{NH}_3} ligands are neutral, so the complex's $+3$ charge is entirely due to cobalt: $x=+3$. Cobalt's atomic number is $Z=27$ and $\text{CN}=6$. $\text{EAN} = 27 - 3 + 2(6) = 24 + 12 = 36$. (b) In $[\text{Ni}(\text{CO})_4]$, $\text{CO}$ is neutral and the complex is neutral overall, so nickel is in the zero oxidation state: $x=0$. Nickel's atomic number is $Z=28$ and $\text{CN}=4$. $\text{EAN} = 28 - 0 + 2(4) = 28+8=36$. Both complexes reach exactly 36, the atomic number of krypton — the same target value as $[\text{Fe(CN)}_6]^{4-}$ from the worked example, despite three ent …

Determine each metal's oxidation state from the ligand charges and the complex's overall charge, then substitute Z, x, and …

Assuming nickel is automatically $+2$ in every complex (a common default) rather than checking the actual ligand c …