Consider the specific alkaline earth metal ion that acts as the universal cofactor for ATP-utilizing — s Block Elements Chemistry Question

💡 Solution & Explanation

The metal is Magnesium ($Mg$, atomic number 12). Its biological state is the $Mg^{2+}$ ion. The electronic configuration of $Mg$ is $1s^2 2s^2 2p^6 3s^2$. The $Mg^{2+}$ ion loses both $3s$ electrons, becoming isoelectronic with Neon ($1s^2 2s^2 2p^6$). Therefore, the $n=3$ shell is completely empty, containing 0 electrons.