Electron pairs

In most cases, in the outer electron shell of a (non) charged ion, eight electrons are present.
(The case with only two electrons in the K shell is not considered here.)

State 1
The electrons repel each other due to their negative charge. That is why can be expected,
they take positions as far away as possible from each other in a electron shell,
being in the eight vertices of a cube.

State 2
However, about a century ago Gilbert Lewis developed the theory,
the eight electrons would dwell as pairs in the four vertices of a tetraeder.
Electron pairs, most of the cases displayed as a hyphen, are important
for the (organic) chemical bonds in molecules.

It is to be expected, the electrons possess more electrical energy in state 2
than in state 1, provided that the ion exists in free state.
However, in case of a bond state 2 has nevertheless a lesser energy. (??)

The two electrons in a pair always have opposite spins (↑↓)

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