GENERAL KNOWLEDGE

Detailed explanation-1: -In general, atoms are most stable, least reactive, when their outermost electron shell is full. Most of the elements important in biology need eight electrons in their outermost shell in order to be stable, and this rule of thumb is known as the octet rule.

Detailed explanation-2: -The quantum states of those valence orbitals are stable, in that there is little interaction with the other electrons. Since there are already filled orbitals, electrons will want to bind to complete the shell because as it happens extra binding energy is available. With a full shell maximum binding occurs.

Detailed explanation-3: –An atom is chemically stable if its outer energy level (valence level) is completely filled with electrons. (8 electrons)-Energy levels are filled by elements gaining, losing, or sharing electrons.

Detailed explanation-4: -Some atoms become more stable by gaining or losing an entire electron (or several electrons). When they do so, atoms form ions, or charged particles. Electron gain or loss can give an atom a filled outermost electron shell and make it energetically more stable.

Detailed explanation-5: -Atoms that have less than eight electrons in their outer shell are unstable. Helium, however, is stable even though it has less than eight electrons, since its outer shell is full with two electrons.