Chapter 12: Solids and Modern Materials

A selection of flashcards covering key concepts from Chapter 12 on solids and modern materials.

What are the four types of solids mentioned in the lecture?

Metallic solids, Ionic solids, Covalent-network solids, and Molecular solids.

What distinguishes crystalline solids from amorphous solids?

Crystalline solids have repeating patterns of atoms, while amorphous solids do not have repeating patterns.

What is a unit cell?

The simplest repeating arrangement of atoms in a crystal.

How many basic lattice types are there, and what modifications can occur?

There are 7 basic lattice types, with modifications like body-centered and face-centered lattices.

What is the characteristic feature shared by all semiconductors?

Semiconductors have a band gap that allows them to conduct electricity under certain conditions.

What is doping in the context of semiconductors?

Doping is the process of adding impurities to a semiconductor to improve its conductivity.

What properties do ionic solids exhibit?

Ionic solids are hard and brittle with very high melting and boiling points.

What is the difference between substitutional and interstitial alloys?

In substitutional alloys, a second element takes the place of a metal atom, while in interstitial alloys, a second element fills spaces in the lattice of metal atoms.

What are the two types of semiconductors?

Elemental semiconductors made of pure elements with 4 valence electrons, and compound semiconductors made of two elements with an average of 4 valence electrons.

What is the relation between bond order and bond strength?

Higher bond order indicates stronger bonds and more stable molecules.

How can you identify a material as a conductor, semiconductor, or superconductor?

By analyzing a resistivity vs temperature curve.

What is a band gap in semiconductors?

The energy difference between the valence band and the conduction band.

How do metallic bonding and the 'sea of electrons' model explain metal properties?

The 'sea of electrons' allows for good electrical and thermal conductivity, ductility, and malleability.

What makes nanoparticles unique regarding energy gaps?

Nanoparticles have tunable band gaps, allowing their properties (like color) to change with size.

Why do ionic solids have high melting points?

Because they are held together by strong electrostatic forces between cations and anions.

What is the bond order of O2?

The bond order of O2 is 2, indicating a double bond.