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Neon is $\ce{K^2 L^8}$, Argon is $\ce{K^2 L^8 M^8}$, Krypton is $\ce{K^2 L^8 M^{18} N^8}$,

But Xenon is $\ce{K^2 L^8 M^{18} N^{26}}$ and radon $\ce{K^2 L^8 M^18 N^{32} O^{26}}$ They don't follow octate rule but they are stable. How? And....

Erbium is $\ce{K^2 L^8 M^{18} N^{32} O^8}$
It follows Octate rule but not stable. Why?

Maurice
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Veeraraghavan
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  • Becaust the octet rule is a simple rule of thumb, that works for many common elements and compounds, but not (strictly) for all of them. Why are you excluding Helium from your list of noble gases? Exactly. – Karl Jan 28 '23 at 14:58
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    Please check your orthography and grammar. – Karl Jan 28 '23 at 14:59
  • Strictly speaking, the octet rule works well for the ten first elements. In the series Na - Cl, there are already exceptions to the rule, like sulfur in covalent $\ce{SF6}$ – Maurice Jan 28 '23 at 15:16

1 Answers1

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Some of your electron configurations are wrong.

Xenon has 18 $N$ electrons ($s+p+d$ sublevels full) and eight $O$ electrons ($s+p$ sublevels full). Radon has 18 $O$ and 8 $P$. Erbium does not have all the $f$ subleblvels full and ends up with $N^{30}O^8P^2$.

You may want to look up the Aufbau Principle. It's imperfect but more accurate than the shell-by-shell ordering you assume. Basically, when you have more than one electron the repulsions between electrons raises the energy of sublevels that have higher angular momentum and don't get close to the nucleus, and then they overlap with lower angular momentum orbitals of what you thought were higher shells.

Oscar Lanzi
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