The-Octet-Rule.pptx

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1. The Octet Rule

2. The octet rule in chemistry is the principle that bonded atoms share their eight outer electrons. (A pair of electrons that is shared between two atoms is called a bond pair. A pair of electrons that is not shared between two atoms is called a lone pair.) This gives the atom a valence shell resembling that of a noble gas. They have completed outer electron shells, which make them very stable.

3. Why Elements Follows the Octet Rule? Atoms follow the octet rule because they always seek the most stable electron configuration. Following the octet rule results in completely filled s- and p- orbitals in an atom's outermost energy level. Low atomic weight elements (the first 20 elements) are most likely to adhere to the octet rule.

4. A Lewis electron dot diagram may be drawn to illustrate the octet rule.

5. Limitations of Octet Rule : (1) Hydrogen with 1 electron attains stability by sharing, gaining or losing 1 valence electron. It does not need to complete octet to attain stability. Also, He has only 2 electrons and is stable. (2) Incomplete octet: In certain molecules such as BeH 2 , BeCl 2 , BH 3 , BF 3 , the central atom has less than 8 electrons in its valence shell, yet the molecule is stable. (3) Expanded octet: In certain molecules such as PF 5 , SF 6 , IF 7 , H 2 SO 4 , the central atom has more than 8 valence electrons, yet the molecule is stable.