I know the general scheme for notating electronic configurations is (with s and p orbitals) [noble gas core]nsel.$n$pel. etc., where $n$ is the principal quantum number and el. is the number of electrons occupying that subshell, e.g. carbon: [He]2s22p2.

Now, how do you include hybrid orbitals? The problem arises because some hybrid orbitals already have superscript numbers (sp2, sp3 …) – how do you differentiate between these superscript numbers and those denoting how many electrons fill that orbital? If I were to write out the electronic configuration for the hybridised carbon atom in $\ce{CO2}$, this would not be a problem: [He]2sp22p2, but what about the carbon atom in $\ce{CH4}$, which has sp3 orbitals? Would you write [He]2sp3, 4 or [He]2sp34 or something else?


1 Answer 1


The electronic configuration concept does not really extend itself well to hybrid orbitals, because these are best considered mathematical concepts only. However, the problem is easily solveable:

Always use brackets when dealing with hybrid orbitals.

Even your $\ce{CO2}$ case is potentially misleading: I misread it once as $\mathrm{2s^1\ 2p^2}$. It is best to show what belongs together with: $\mathrm{[He]\ 2(sp)^2\ 2p^2}$ or, for methane: $\mathrm{[He]\ 2(sp^3)^4}$.

  • $\begingroup$ What description of bonding is anything more than a mathematical concept? $\endgroup$
    – ron
    Dec 25, 2015 at 3:02
  • $\begingroup$ @ron True, but turn it around. The orbitals of an atom in ground state are about the closest we can get to quantumphysical reality. I didn’t want to stress that other descriptions of bonds be less mathematical but rather that the ground state is less so. $\endgroup$
    – Jan
    Dec 25, 2015 at 15:27

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