Chemistry; CHAPTER-4 : chemical bonding and molecular structure

Kössel-Lewis Approach

A method for explaining chemical bonding based on the inertness of noble gases and the octet rule.

Octet Rule

The principle that atoms tend to form bonds until they are surrounded by eight valence electrons.

VSEPR Theory

A theory that predicts the geometry of molecules based on repulsion between electron pairs in the valence shell.

Valence Bond Theory

A theory that explains the formation of covalent bonds through the overlap of atomic orbitals.

Resonance Structures

Different Lewis structures for a molecule that represent the same arrangement of atoms but differ in the distribution of electrons.

Covalent Bond

A chemical bond formed by the sharing of electrons between two atoms.

Ionic Bond

A chemical bond formed through the electrostatic attraction between positive and negative ions.

Lewis Structures

Diagrams that show how atoms are bonded in a molecule and the arrangement of lone pairs of electrons.

Hybridization

The process of mixing atomic orbitals to form new hybrid orbitals suitable for pairing of electrons to form chemical bonds.

Dipole Moment

A measure of the separation of positive and negative charges in a molecule, indicating its polarity.

Formal Charge

The difference between the number of valence electrons in a free atom and the number assigned to it in a Lewis structure.

Electronegativity

The ability of an atom in a molecule to attract shared electrons.

Hydrogen Bond

A weak bond formed when a hydrogen atom covalently bonded to an electronegative atom is also attracted to another electronegative atom.

Lattice Enthalpy

The energy required to separate one mole of an ionic solid into gaseous ions.

Bond Length

The equilibrium distance between the nuclei of two bonded atoms.

Bond Angle

The angle formed between three atoms across at least two bonds.

Bond Order

The number of shared electron pairs between two atoms; determines bond strength and length.

Sigma Bond (σ)

A covalent bond formed by the direct overlap of orbitals along the axis connecting two bonding nuclei.

Pi Bond (π)

A covalent bond formed by the sidewise overlap of two p-orbitals.

Molecular Orbital Theory

A theory that describes the distribution of electrons in molecules using molecular orbitals rather than atomic orbitals.

Electron Gain Enthalpy

The change in energy when an electron is added to a neutral atom in the gas phase.

Formal Charge Calculation Formula

Formal charge (F.C.) = (valence electrons) - (non-bonding electrons) - (1/2 bonding electrons).

Stable Configuration

The arrangement of electrons in atoms or molecules that leads to minimal energy and maximum stability.