A highly unstable complex ion obeys Sidgwick's Effective Atomic Number (EAN) rule. The atomic number — Coordination Compounds Chemistry Question

💡 Solution & Explanation

The EAN rule states: $EAN = Z - \text{Oxidation State} + 2 \times (\text{Coordination Number})$. For the complex $[AuCl_6]^y-$ to obey the rule, EAN must be 86. $86 = 79 - x + 2(6) \Rightarrow 86 = 79 - x + 12 \Rightarrow 86 = 91 - x \Rightarrow x = +5$. The oxidation state of Gold is $+5$. The charge on the complex $y$ is the sum of the oxidation state of the metal and the charges of the ligands. $y = +5 + 6(-1) = -1$. The absolute value is $1$.