GEOLOGY

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: -Atoms will react to get in the most stable state possible. A complete octet is very stable because all orbitals will be full. Atoms with greater stability have less energy, so a reaction that increases the stability of the atoms will release energy in the form of heat or light.

Detailed explanation-3: -The properties of an element are determined by its outermost electrons, or those in the highest energy orbital. Atoms that do not have full outer shells will tend to gain or lose electrons, resulting in a full outer shell and, therefore, stability.

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.