We all know atoms want to stabilize by having an octet or duplet configuration. But if you see nitrogen which has an electron configuration of $\ce{2p^3}$. It has half filled p orbital, so it is technically stable, isn't it? Then why don't elements like oxygen form a monovalent oxygen ion?

By similar logic, sodium has $\ce{3s^1}$ configuration which should also be stable because it has a half filed orbital. But sodium is reactive as we know.

Can you please point out the flaw in my argument?

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    $\begingroup$ Nitrogen which has am electron configuration of 2p3. It has half filled p orbital, so it is technically stable right? No, a N atom is not stable in that two such atoms will form a molecule $\ce{N2}$. $\endgroup$
    – MaxW
    Commented Jul 6, 2018 at 18:23
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    $\begingroup$ Stability is relative. A half-filled orbital configuration is more stable than usual, but not as stable as an octet, etc. $\endgroup$ Commented Jul 6, 2018 at 18:28

1 Answer 1


As also pointed out in the comments, there is no such thing as absolute stability. One species is stable only with respect to another species.

You may have come across the fact - that half-filled configurations are "stable" - while studying ionization enthalpy/electron gain enthalpy, or the electronic configuration of $\ce{3d}$ elements. Pay careful attention: the half-filled configuration is "stable", but only with respect to the neighbouring configurations. That is to say, the $\ce{2p^3}$ configuration is much stable than $\ce{2p^4}$ or $\ce{2p^2}$. Yet, $\ce{2p^3}$ is still very less stable than $\ce{2p^6}$. This is why, in nature, nitrogen prefers to exist in diatomic molecules, so as to complete its octet.

Now for the fully-filled $\ce{3s^2}$ configuration (sodium anion, aka "sodide"): again, note that the sodium cation is way more stable than the sodium anion, as the former has a fully filled octet, while the latter doesn't. (Sodide has indeed been formed, but by using special techniques only. See Wikipedia).

Also see: Why are atoms with eight electrons in the outer shell extremely stable? and Why do atoms "want" to have a full outer shell?

  • $\begingroup$ Well, I think there may be need to do a bit of debunking of debunking. Inherent instability is quite a thing and you seem to be rather talking about reactivity. $\endgroup$
    – Mithoron
    Commented Jul 7, 2018 at 16:05
  • $\begingroup$ @Mithoron Could you please elaborate a bit more on your statement: " Inherent instability is quite a thing"? $\endgroup$ Commented Jul 8, 2018 at 1:34
  • $\begingroup$ If something is inherently unstable, it breaks down by itself. $\endgroup$
    – Mithoron
    Commented Jul 8, 2018 at 20:49

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