| The sodium ion has the same electron configuration as neon, the noble gas immediately before it on the Periodic Table. |
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| Indeed, potassium is similar in chemical properties to sodium, which is consistent with its analogous electron configuration. |
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| The chemical, metallurgical, and physical behaviours of the rare earths are governed by the electron configuration of these elements. |
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| At this point it should be noticed that the second noble gas, neon, has a closed-shell electron configuration, as does the first noble gas, helium. |
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