Magnesium has a di-electron making up its 3rd shell, with two full core shells within that have the identical configuration to neon. Given its larger size, the 3s2 di-electron is not as well-bound as the 2s2 di-electron on beryllium. Magnesium will therefore donate its valence electrons more readily than beryllium, but it will not be as reactive in doing so as the metals below it in Group II such as calcium, strontium, or barium.
As we saw in the case of neon, the 2nd shell orbitals are more like spherical tetrahedra, and the 3rd shell is a di-electron in a spherical s-orbital. These orbitals represent phase-locked, resonant, coherent, harmonic, stationary waves.
Magnesium is more willing to lose its two valence electrons in an ionic interaction than is beryllium because it is larger, and it will lose both at the same time in order to reach the stability of a full 2nd shell. This is the same electron configuration as the 2s22p6 noble gas configuration of neon — a multi-di-electron state with two concentric full shells. That is why magnesium forms a 2+ ionic state.
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