Chem unit 6

Molecular Geometry

The 3-D arrangement of atoms that constitute a molecule.

Square planar

A molecular geometry where 4 atoms are bonded to a central atom in a square formation.

Linear

A molecular geometry where atoms are arranged in a straight line.

Nonpolar molecules with lone pairs

Molecules with the same terminal atoms and lone pairs on the central atom are nonpolar.

Valence electrons

The total number of outer shell electrons that are available for bonding.

Octet Rule Exceptions

H and He are satisfied with 2 electrons; B, Be, and Al can have less than 8 electrons.

Expanded octet

When heavier elements (3rd row and below) exceed the octet rule using empty d orbitals.

Resonance

Occurs when a double or triple bond can be in different positions but has the same structure.

Polyatomic ions

Ions that consist of two or more atoms that are bonded together and have a charge.

Hybridization

The combining of two or more orbitals of nearly equal energy within the same atom.

Steric Area

The number of lone pairs and bonds around the central atom’s electron region.

Cohesion

Attraction of molecules in a liquid to each other due to intermolecular forces.

Surface tension

The tendency of liquids to minimize their surface area due to intermolecular forces.

Viscosity

Resistance to flow within a liquid.

Capillary Action

The ability of a liquid to rise in a narrow tube due to adhesion and cohesion.

Intermolecular forces

Attractive forces between separate molecules, occurs in substances with covalent bonds.

London dispersion forces

Weak intermolecular forces between nonpolar molecules caused by temporary dipoles.

Dipole-Dipole Forces

Attraction between opposite partial charges in polar molecules.

Hydrogen Bonding

A strong type of dipole-dipole interaction involving hydrogen and electronegative elements.

Ion dipole interaction

Attraction between ions and polar molecules.

Vapor pressure

The pressure exerted by gas molecules of a substance on the walls of a closed container.

Evaporation factors

Factors affecting evaporation include temperature and surface area.

Potential energy

The stored energy in molecules related to their position in a substance.

Kinetic energy

The energy of motion of molecules.

Phase diagram

A graphical representation of the phases of a substance as a function of pressure and temperature.

Critical point

The max temperature and pressure where the substance can exist as a liquid.

Amorphous solid

A solid with considerable disorder in its structure.

Crystalline solid

A solid with a highly regular arrangement of particles.

Unit cell

The smallest repeating unit of a crystal lattice.

Lattice

A 3D system of points indicating the positions of ions, atoms, or molecules.

Atomic solids

Solids that consist of atoms at each lattice point.

Ionic solids

Solids with ions occupying lattice points.

Molecular solids

Solids with discrete covalently bonded molecules at lattice points.