If helium does not obey the octer rule then why do its atom not react?

Answer 1

The octet rule is based on two principles:

1. Stability of completely filled atomic orbitals

2. Electrostatic affinity of oppositely charged particles

Most atoms will either gain, or lose (depending on the position on the table), electrons to obtain the noble "gas configuration" or "octet". This is works well for atoms who are two or three spaces away from a noble gas on the Periodic Table, since these atoms will only need to gain two or three electrons to satisfy the octet rule.

As we get farther from the noble gases, however, it becomes increasingly difficult to gain more electrons, because the unbalanced charge that results from the additional electrons destabilizes the atom and the energy required to add that next electron becomes higher with each addition until it is actually more energetically favorable to lose electrons (this is why some species exist predominantly as ions).

In the specific case of hydrogen, we notice that it has only one positively charged proton. Since electrons bear equal but opposite charges to protons, it is now understandable that H could host only a few extra electrons while maintaining appreciable stability.

Helium can be analyzed the same way. In this case, we also note that Helium is in the noble gas column of the periodic table, so it must display qualities of a noble gas itself. He is, in fact, a very stable monoatomic molecule and exists naturally as He gas at in standard conditions.

As H and He has K shell they can accommodate only two electrons only,so unable to be octet. The magic numbers are-2,8,8,18,18,32

Answer 2

Helium has completely filled s orbital. Hence it is stable and unreactive.

Answer 3

Helium's only shell is still full. The 1st shell, Made up of a 1s atomic orbital. can only hold 2 electrons. Making it a noble gas.