Neon has two full electron shells — an inner core 1s shell, and a 2s shell containing a full p-orbital resonance. With 6 electrons in a 2p orbital, neon is believed to achieve stability with octahedral symmetry, and its 2s electrons can unhybridize and return to their preferred spherical di-electron state (see below). It is proposed in the theory of Sub-Quantum Chemistry, however, that neon is more stable with a tetrahedral valence shell of 4 di-electrons (shown here).
In either case, its high degree of symmetry, with all electrons paired, renders neon, like helium, unable to bond, and therefore chemically unreactive.
Intuitively, it seems more stable to consider the electron structure of neon (and of the full n=2 shell) as a tetrahedral arrangement of four di-electrons since it involves a greater degree of field cancellation than a full p-orbital with a single electron occupying each lobe.
The small spheres in these diagrams are only meant to indicate the directions of the orbital lobes. These lobes are not spheres. Only s-orbitals are spherical. The outer spheres indicate the center of each orbital’s focus and region of highest electron density. The orbitals themselves are more like spherical tetrahedra that can only occupy volume within their shell. The entire shell will be filled with electron density. It will be highest at the center of the face of each orbital (as in the traditional sp3 lobe shapes) and will decrease toward the nodal regions between orbitals, where electron density will be lowest (though not necessarily zero). These lobes represent phase-locked, resonant, coherent, harmonic, stationary waves.
In the case of argon (Ar), since there are two concentric tetrahedral shells, they will align to form an antiparallel nested tetrahedral geometry because this minimizes repulsion between layers. The place of lowest electron density — where the nodal vertices intersect — on one shell is set against the highest electron density at the center of a face on the adjacent concentric shell. This is therefore the lowest energy state that nested tetrahedral shells can achieve.
Unlike fluorine, neon is one of the two most unreactive elements on the periodic table. One of its primary uses (along with other noble gases) is as a gas in lighting (glow discharge) tubes, and it gives neon signs their characteristic bright red color.
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