How do we know for certain that atoms can’t have more than 8 maximum outermost electrons when atoms form chemical bonds? Is there any research being done to see why atoms prefer the octet rule?
When atoms form chemical bonds, they share or exchange electrons to become stable. Atoms are most stable when they have a full outermost shell of electrons. The octet rule says that atoms tend to gain, lose, or share electrons to have 8 electrons in their outermost shell because that’s a very stable configuration.
The octet rule is based on observations of how different elements behave and how their electrons are arranged. However, there are exceptions to this rule, and scientists are still studying why certain atoms can have more than 8 electrons in their outermost shell and still be stable.
Well we know for sure from experimentation that some molecules don’t obey the octet rule, and a whole class of elements, the transition metals, obey an 18-electron rule rather than the octet rule. But the general principle that certain electron orbital configurations are more stable and lower-energy states, and therefore atoms will readily undergo reactions to achieve those states, generally holds true. The least reactive elements on the periodic table (the noble gases) already obey the octet rule, and the most reactive elements are those that only need a little energy (being only a few electrons away from a noble gas configuration in either direction) to get to such a configuration.
The octet rule is a pretty old and simplified model for chemical bonding. It is only applicable for second- and third-row main-group elements in the first place and even there you‘ll find many exceptions (for example: borane clusters, pentacoordinate carbon atoms). Still, many small molecules and most organic compounds follow the rule, and since it is easier to learn than the modern, more accurate bonding concepts, it is still widely taught.
Current research on chemical bonding is done with either molecular-orbital theory or valence-bonding theory, which are both based on quantum mechanics and were introduced in the early 1930s. Both theories have no need for an octet rule, and they are much more complicated. Sometimes, researchers still study whether a molecule obeys or violates the octet rule, but since 1) the concept has become redundant, and 2) many exceptions have already been found, this is no longer an exciting field of research.
You see, we know how atoms work by solving very complicated quantum mechanics equations (in the past by hand!) And we could learn things like the orbital shape and other useful properties.
Now, solving everytime equations is hard and most of the time in chemistry there are a lot of shortcuts to make life easier. The octet rule is one of those, and if you look at the f and d block, or the haufbau filling rules you see that the octet is not so much set in stone!
Also, in the past by looking ad atom emission and absorption spectra we could find out quite accurately the energy of the levels, and it his way we can really see how electrons occupy atomic orbitals !
They did this research almost a hundred years ago. The s and p electronics are the most active chemically and there are 8 of those in each level. The electron configuration if the nearest noble gas is usually the most stable chemically.
This is especially true of the non-metallic elements in the top-right corner which are most often present in large organic molecules. C,N,O and the halogens. P and S are interesting exceptions! They can have 10 and 12 instead of just 8.