Question

For an atom to attain stable configuration,it should have 8 electrons in the outermost shell.
But what about Helium?

Answer 1

• A Noble Gas does not need to have eight electrons to be classed as such - it simply must have a full outer shell. The first shell can only hold two electrons, which is same in helium has, so helium is a Noble Gas.
• The second and third shells hold eight electrons, which is why other noble gases can be seen as having eight electrons. However no Noble Gases have eight electrons in total - just eight in the outer shell, as the shells fill from the inside out.
• So, He has only 2 electrons in ite outer mpost orbitals, because its atomic number is 2.