Lecture 5 (BME 296)

Cation

A positively charged ion that must be next to anions to maintain electrical neutrality in a compound; smaller than anions due to the loss of electrons

Anion

A negatively charged ion; larger than cations due to the gain of electrons

Electroneutrality

The condition when the total positive charge is equal to the total negative charge in a compound.

Interstitial defect

A point defect where an atom occupies a space in the lattice that is normally unoccupied.

Vacancy defect

A point defect where an atom is missing from its lattice site.

Schottky defect

A defect that occurs when vacancies are formed in both cations and anions to maintain electroneutrality.

Frenkel defect

A defect created by the displacement of an atom from its lattice site to an interstitial site, maintaining electroneutrality.

AX crystal structure

A crystal structure consisting of equal amounts of cations (A) and anions (X) with the same charge and required for stability.

AmXp crystal structure

A crystal structure where the cation (A) and anion (X) have unequal charges.

Degree of polymerization

The number of repeating units in a polymer (n)

Polydispersity index (PI)

A measure of the distribution of molecular weight in a given polymer sample.

Thermoplastic polymer

A polymer that can be melted and remolded upon heating.

Thermosetting polymer

A polymer that, once set, cannot be remolded.

Isotactic configuration

A polymer configuration where side groups are arranged on the same side of the chain.

Syndiotactic configuration

A polymer configuration where side groups alternate positions on either side of the chain.

Atactic configuration

A random arrangement of side groups in a polymer chain.

Addition polymerization

A type of polymerization where monomers add together without the loss of any atom.

Condensation polymerization

A type of polymerization that involves the elimination of a small molecule (like water) during the formation of the polymer.

Polymer size

The molecular weight of the chain