Imagine the bonding as reaching an equilibrium where Mg2+ bonds and then dissociates in a repeating cycle. If you flood that solution with Na+, the chances for

Imagine the bonding as reaching an equilibrium where Mg2+ bonds and then dissociates in a repeating cycle. If you flood that solution with Na+, the chances for Mg2+ to bond after dissociating are lower when an excess of Na+ is doing the same thing, and a new equilibrium is reached.