Question

Why are there only eight electrons in the outer shell?

Answer 1

Hint: We know that the atom consists of three basic particles which are protons, electrons, and neutrons. The atom is the smallest particle in which protons and neutrons are present in the center and electrons revolve around it.

Complete answer:
Atoms of various elements tend to gain, lose or share valence electrons during the formation of molecules such that there are eight electrons or octets in their valence shells. This octet rule or electronic theory of the chemical bonding was proposed by Kossel and Lewis. The octet rule refers to a crucial principle that the atoms which have bonded share eight outer electrons. This certainly implies that the atom’s valence shell contains a resemblance with noble gas. The octet rule states that the atoms prefer to have eight electrons only in their full outer shells. For achieving eight electrons in their outer shells, atoms would gain or lose the valence electrons. Furthermore, the atom does this by bonding with one another. Moreover, these bonding can be between the same identical element or with different elements.
Atoms seem to be most stable with a whole outer shell one containing eight electrons when the primary, contributive to what's widely referred to as the octet rule. Its outer electrons, or those within the highest energy orbital, confirm the properties of Associate in Nursing atoms. This is because of the quantum nature of the atoms, wherever electrons are a unit organized into shells: there is a pair of electrons within the first referred to as the K shell, eight within the second (L-shell), eighteen within the third (M shell). In most cases, atoms fuse into molecules by making an attempt to induce valence electrons crammed a shell full.

Note:
Remember that the atoms don’t achieve stability only by donating or accepting the valence electrons. Sometimes stability is achieved from various types of bonds by sharing the electrons. A chemical bond is basically the force of attraction between any two atoms in a molecule required to maintain stability.