Editing Octet rule (section)

== Other rules ==
The octet rule is only applicable to [[main-group element]]s. Other elements follow other [[electron counting]] rules as their [[valence electron]] configurations are different from main-group elements. These other rules are shown below:
{| class="wikitable"
|-
!Element type||First shell||p-block<br/>([[Main-group element|Main group]])||d-block<br/>([[Transition metal]])
|-
!Electron counting rules
|Duet/Duplet rule
|Octet rule
|18-electron rule
|-
!Full valence configuration
|s<sup>2</sup>
|s<sup>2</sup>p<sup>6</sup>
|d<sup>10</sup>s<sup>2</sup>p<sup>6</sup>
|}
* The '''duet rule''' or '''duplet rule''' of the first shell applies to H, He and Li—the noble gas [[helium]] has two electrons in its outer shell, which is very stable. (Since there is no 1''p'' subshell, 1''s'' is followed immediately by 2''s'', and thus shell 1 can only have at most 2 valence electrons). [[Hydrogen]] only needs one additional electron to attain this stable configuration, while [[lithium]] needs to lose one.
* For [[transition metal]]s, molecules tend to obey the '''[[18-electron rule]]''' which corresponds to the utilization of valence ''d'', ''s'' and ''p'' orbitals to form bonding and non-bonding orbitals. However, unlike the octet rule for main-group elements, transition metals do not strictly obey the 18-electron rule and the valence electron count can vary between 12 and 18.<ref>{{cite book |editor1-last=Frenking |editor1-first=Gernot|editor2-last=Shaik |editor2-first=Sason|title=The Chemical Bond: Chemical Bonding Across the Periodic Table |publisher=Wiley -VCH |date=May 2014 |chapter=Chapter 7: Chemical bonding in Transition Metal Compounds |isbn=978-3-527-33315-8}}</ref><ref>{{cite journal
| title = The Nature of the Bonding in Transition-Metal Compounds
| first1= Gernot |last1=Frenking |first2=Nikolaus |last2=Fröhlich
| journal = [[Chemical Reviews|Chem. Rev.]]
| year = 2000
| volume = 100
| issue = 2
| pages = 717–774
| doi = 10.1021/cr980401l
| pmid= 11749249}}</ref><ref>{{cite journal
| title = Prediction of the Geometries of Simple Transition Metal Polyhydride Complexes by Symmetry Analysis
| first1= Craig |last1=Bayse |first2=Michael |last2=Hall
| journal = [[Journal of the American Chemical Society|J. Am. Chem. Soc.]]
| year = 1999
| volume = 121
| issue = 6
| pages = 1348–1358
| doi = 10.1021/ja981965+
}}</ref><ref>{{cite journal
| title = Structure and bonding in homoleptic transition metal hydride anions
| first= R.B. |last= King 
| journal = Coordination Chemistry Reviews
| year = 2000
| volume = 200–202
| pages = 813–829
| doi = 10.1016/S0010-8545(00)00263-0
}}</ref>