Properties of Solids

Physical properties

• While solid has definite shape and volume; it does have various other properties that can be very different. Such as density, colour, melting points, etc

Pg. 119

Ionic solids

• Lots found in nature as rock and mineral deposits:– Sodium chloride (salt)– Potassium chloride (potash)

• Also found at home:– Household cleaners (contains sodium hydroixde)

• Other examples:– Rust (iron (III) hydroxide)– Tarnish (silver sulfide)

Cont’d

• Some reactive metals don’t occur in elemental form in nature, they are found as ionic compounds

• Ionic compounds are also used to extract metals from naturally occurring compounds

• For example: iron is the most common metal used but is also very reactive

Formation

• Formation reaction of a metal and nonmetal similar to sodium chloride

• Formation reaction of two compounds• Ionic compound stability is similar to that of

noble gases so it can be suggested that there is a total electron transfer occurring.

A model

• At SATP, all ionic compounds are solid so they must be held together (bonded) in that rigid structure.

• Models show that the ions are arranged in a regular pattern, depending on the size, shapes and charges

• This is called a crystal lattice

Ionic Compounds

• Ionic compounds are brittle – the ions don’t rearrange

• Binary ionic compounds also have medium to high boiling points

• Polyatomic ions have more complex crystal lattices but the ions have covalent bonds so can be treated like an monatomic ion

Metallic Crystals

• Shiny, silvery, flexible solids with good electrical and thermal conductivity

• Hardness varies greatly as well as the melting temperature

• X-Ray diffraction shows that all metals have a continuous and compact crystalline structure

Metal Properties• Metallic bonding – continuous electron clouds– Low electronegativity – loosely holding electrons– Empty valence orbitals explains electron mobility– Strong Electrostatic attraction for bonding– this gives the many different properties to metallic

compounds

Pg. 124

Molecular crystal

• Elements or compounds• Small molecules for solid crystal, low melting

point, not very hard, nonconductors• Properties can be explained by the IMF and

structure

Covalent Network Crystals

• Crystal substances– Diamond and quartz – very hard

• Very hard, high melting point, brittle, insoluble, nonconductors

• Examples – silicon carbide SiC(s) used in sandpaper,

Carbon

• Carbon is extremely versatile with bonding in various ways

Semiconductors

• Crystalline silicon or germanium ‘doped’ with a Group 13 or 15 element

• Little bit of energy to put an electron into a higher orbital and conduct electricity

• Used in transistors, solar cells

Summary

Unit Test Review Summary

• Lewis Formulas• Bonding Theory (types)• Electronegativity • Molecular Formulas (Lewis, structural, sterochemical) • Bonding capacity• VSEPR• Bond and molecular Polarity• Intermolecular Forces

– Isoelectronic Compounds• Boiling points• Properties of Liquids and Solids

Suggested review questions

• Pg. 137 #3, 6, 7, 10, 12, 14• Pg. 138 #21, 25, 28• Pg. 139 #35, 40, 41, 43• Pg. 140 #48, 53, 57• Pg. 141 #60