Which diagram shows the correct distribution of electrons in the electron shells of magnesium atom?

For Magnesium the distribution of electrons is the following; two electrons in shell one, eight in shell two, and two more in shell three.

Magnesium has an atomic number of 12. Now for the first 18 elements we know that the 3rd shell can hold 8 electrons, the 2nd 8 and the first 2.

On Edgenuity is the third option.

where's the diagram?

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