13.3 and Pre-Lab Solids and Sulfur

Properties of Solids Tightly packed particles Dense Not easy to compress Particles vibrate in motion Do not flow Most are crystalline

Crystalline Structures A crystal is a 3D pattern that has a repeating pattern of orderly particles. There are several different types of crystal systems that are classified based on bonding, length of each face, and angle between each face. Figure: 13.11 The overall shape of the crystal is affected by the geometric shape of the particles.

Several unit cells placed on top of one another creates a crystal. The smallest group of particles that retain the geometric shape of the crystal is called the unit cell. Several unit cells placed on top of one another creates a crystal.

Types of Unit Cells Body Centered Cell (atom at each corner and one in center, body) Simple Cubic Cell (atom at each corner) ATOMS Face Centered Cell (atom at each corner and at each face)

Allotropes Elements which exist in two or more different forms in the same physical state. Differ in physical properties and may also differ in chemical activity.

Examples of Allotropes Oxygen Oxygen gas, O2 Ozone, O3 Sulfur We will do this in lab

Carbon Diamond: high density and hard Graphite: low density black, soft, and slippery Buckminsterfullerene (aka buckeyball): 60 carbon rings in hexagon/pentagon patterns. Looks like a soccer ball. Rigid and strong. http://www.ktf-split.hr/glossary/en_o.php?def=allotrope

Non-Crystalline Forms Something that is amorphous Amorphous: lacks structure and has irregular angles Examples rubber, plastics, asphalt, glass

Pre-Lab Key Terms Sulfur can be considered allotropic because it has several forms. Sulfur is also polymorphic. Polymorphic: a single substance that can have more than one crystal form. Isomorphic: different substances that have the same crystal form.

3 Types of Sulfur in Lab Orthorhombic (rhombic)- this form of crystal is very stable and will form S8 rings when heated. Monoclinic-this form is less stable and is formed when sulfur is melted and then cooled slowly. Amorphous (plastic)- this form is very unstable and is formed when boiling sulfur is added to water. This causes the rings of the crystal to break and all structure is lost.