The observer effect in quantum mechanics states that when unobserved, quantum particles such as electrons can simultaneously occupy two different states. In an atom of any element, where there are electrons around the nucleus, this effect is hinted at in some publications:
Electrons can occupy several energy levels, or orbitals, simultaneously. (Scientific American.(2012, October 9). Bringing Schrödinger's Cat to Life. Retrieved from https://www.scientificamerican.com/article/bringing-schrodingers-quantum-cat-to-life/.)
This idea is so weird. It is equivalent of saying that when unobserved, all the electrons of an atom can both be in their normal configuration and be in a totally different configuration. Only the act of observation forces the electrons into their normal configuration. Take the example of neon atom. According to the observer effect, when unobserved, its electron configuration can both be 1s4 2s3 2p3 (one of many possible alternative configurations) and 1s2 2s2 2p6. Only when observed will the electron configuration collapse into its normal version of 1s2 2s2 2p6.
I don't know if this understanding of observer effect on atomic electrons is valid. If it is, there are at least two serious problems. First, the Pauli exclusion principle will break down, because the alternative electron configuration allows more than 2 electrons in the same orbital (specified by the principal quantum number, the angular momentum quantum number, and the magnetic quantum number). Second, the foundation of covalent bonding is that when two or more atoms pool together electrons in orbitals that overlap, the total energy of the system is reduced to the minimum. If the observer effect on atomic electrons is valid, the energy required to maintain the system may get even lower than that in covalent bonding, and then covalent bonding will break down. All that's needed is for each atom to achieve an alternative electron configuration.
Thanks, everybody. I now understand this question better. Yes, the observer effect does apply to atomic electrons by allowing each of them to occupy several orbitals, subshells, or even shells at the same time. However, if we look at all the electrons and summarize their states into an electron configuration scheme, the scheme will still be the same as that obtained through the aufbau principle.