Chapter 4, Section 3Crystal Chemistry

Monday, December 14, 2009

Pages 128 -- 130

Objectives

• Explain how the chemical bonds of a crystal determine the substance’s properties.

• Describe and give examples of mineral crystals.

Vocabulary Word

• Mineral

Mineral Properties

• A mineral is a naturally occurring solid.

• It has a crystal structure and a definite chemical composition.

• A few are elements.

• Most are compounds.

Mineral Properties -- cont’d

• Properties include:• Color• Shininess• Density• Crystal shape• Hardness• Magnetism

Mineral Properties -- cont’d

• Minerals break into regular shapes.• Splits easily easily along fat surfaces and at

sharp angles.• Crystals also grow in characteristic shapes.• All properties depend on its chemical

composition.• Each mineral is different because each has a

different chemical composition.

Bonding in Mineral Crystals

• The arrangement of particles in a mineral and the kind of bonds holding them together determine properties such as crystal shape, hardness, and the way the crystal breaks apart.

An Ionic Crystal

• Example is Halite.• Made of sodium

chloride.• Soft.• Easily dissolved.• Even breaks

QuickTime™ and a decompressor

are needed to see this picture.

Covalent Crystal

• Example is Quartz.• Covalent bonds are

strong.• Won’t dissolve in

water.• Hard• No defined lines of

weakness.

QuickTime™ and a decompressor

are needed to see this picture.

Homework

• Workbook 4.3 (due 12/16)

• No vocabulary quiz!!