The Periodic Table - Compounds and Molecules - Lecture 2

These flashcards cover key vocabulary and concepts related to the periodic table, molecular shapes, bonding theories, and energy changes in chemical reactions.

Valence Shell Electron Pair Repulsion Theory (VSEPR)

A theory that explains the geometry of molecules based on the repulsion between electron pairs around a central atom.

Central Atom

The atom in a molecule that is surrounded by other atoms and is typically the one that dictates the molecular geometry.

Lone Pair (lp)

A pair of valence electrons that are not shared with other atoms and occupy space around the central atom.

Bonding Pair (bp)

A pair of electrons shared between two atoms, contributing to the formation of a covalent bond.

Trigonal Pyramidal

A molecular shape that results from four electron pairs around a central atom with three bonding pairs and one lone pair.

Bent or ‘V-shaped’

A molecular geometry formed when a central atom has two bonding pairs and one or more lone pairs.

Trigonal Bipyramidal

A molecular geometry with five bonding pairs arranged in a shape that has two different types of positions: axial and equatorial.

Octahedral

A molecular geometry where six pairs of electrons are arranged around a central atom, with bond angles of 90 degrees.

Homolytic Bond Fission

A breakage of a covalent bond where each atom involved takes one of the shared electrons.

Bond Energy (BE)

The average enthalpy change needed to break a bond in the gas phase.

Covalent Bonds

Chemical bonds formed by the sharing of electron pairs between atoms.

Enthalpy (∆H)

The heat content of a system at constant pressure, often involved in reactions indicating energy changes.

Lewis Structure

A diagram that shows the bonding between atoms and the lone pairs of electrons in a molecule.

Energy of Bond Formation

The energy required to form a bond between atoms, typically negative as energy is released during formation.

Energy of Bond Dissociation

The energy required to break a bond, typically positive as energy is absorbed during dissociation.

Electronegativity

A measure of an atom's ability to attract and hold onto electrons.

Multiple Bonds

Bonds in which two or more pairs of electrons are shared between atoms, such as double or triple bonds.

Axial and Equatorial Positions

Positions of atoms in a trigonal bipyramidal structure where axial atoms are perpendicular to the equatorial atoms.

Repulsion Order

The hierarchy of repulsion types in VSEPR theory: lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair.

Bond Cleavage

The breaking of bonds between atoms in a molecule, which can be homolytic or heterolytic.