Chemical Bonding and Structure - Covalent bonding

A covalent bond is the electrostatic attraction between a shared pair of electrons and the positively charged nuclei of the atoms involved.

The octet rule states that atoms tend to gain, lose, or share electrons to achieve a stable electron configuration of eight valence electrons, similar to a noble gas. Exceptions include incomplete octets (e.g., $BeCl_2$, $BF_3$) and expanded octets for elements in Period 3 and below (e.g., $PCl_5$, $SF_6$).

Bond polarity is determined by the difference in electronegativity ($\Delta\chi$) between atoms. A polar covalent bond occurs when $0.5 < \Delta\chi < 1.7$, leading to a dipole moment represented by $\delta+$ and $\delta-$.

Valence Shell Electron Pair Repulsion (VSEPR) theory predicts molecular geometry based on minimizing repulsion between electron domains. Total domains include both bonding pairs and lone pairs.

Resonance occurs when more than one valid Lewis structure can be drawn for a molecule (e.g., $O_3$, $C_6H_6$, $CO_3^{2-}$). The actual structure is a resonance hybrid with delocalized electrons.

Sigma ($\sigma$) bonds are formed by the head-on overlap of atomic orbitals along the internuclear axis. Pi ($\pi$) bonds are formed by the sideways overlap of $p$-orbitals above and below the internuclear axis.

Hybridization involves the mixing of atomic orbitals (such as $s$ and $p$) to form new hybrid orbitals ($sp, sp^2, sp^3$) that are degenerate (equal in energy).

Giant covalent structures like diamond, graphite, graphene, and $SiO_2$ have high melting points and varying electrical conductivities based on electron delocalization.