Chemical Bonding - Octet Rule-advanced

The Octet Rule states that atoms of elements combine to form molecules in such a way that each atom has eight electrons in its valence shell, achieving the stable electronic configuration of a noble gas.

The Duet Rule is a specific case for elements like Hydrogen ($H$), Lithium ($Li$), and Beryllium ($Be$), which strive to achieve two electrons in their outermost shell, resembling the Helium ($He$) configuration.

Valency is the combining capacity of an atom, determined by the number of electrons it needs to lose, gain, or share to complete its octet. For atoms with $v$ valence electrons, if $v \le 4$, valency is $v$; if $v > 4$, valency is $8 - v$.

Lewis Dot Structures are diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons that may exist. Valence electrons are represented as dots around the chemical symbol.

Ionic (Electrovalent) Bonding occurs when one atom transfers electrons to another. For example, $Na$ ($2, 8, 1$) loses an electron to $Cl$ ($2, 8, 7$) to form $Na^+$ and $Cl^-$, both achieving the octet configuration.

Covalent Bonding involves the sharing of electron pairs between atoms. In $Cl_2$, each Chlorine atom shares one electron to complete their respective octets.

Advanced Exceptions - Incomplete Octet: In some compounds like $BCl_3$ or $BeH_2$, the central atom has fewer than 8 electrons (e.g., Boron in $BCl_3$ has only 6 electrons).

Advanced Exceptions - Expanded Octet: Elements in the 3rd period and beyond (like $P$, $S$, $Cl$) can accommodate more than 8 electrons due to the availability of $d$-orbitals. Examples include $PCl_5$ (10 electrons) and $SF_6$ (12 electrons).