Metallic and Ionic Solids Section 13.4, Exams of Chemistry

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Solids

Adapted from a presentation by Dr. Schroeder, Wayne State University

Types of Crystalline Solids

Type Attractive forces examples

Molecular IMF’s Ice, dry ice, sugar

Ionic Ionic bonds NaCl, CaF 2 , ZnS

Metallic Metallic bonds Na, Fe, Zn, Au

Covalent network Covalent bonds Diamond, graphite, gemstones

Example of a

molecular solid:

ice

Note: the regular arrangement of the crystal maximizes the H-bonding (4/molecule) and as a side effect actually causes the molecules to move further apart than in the liquid state, thus rendering ice less dense than liquid water – ice floats. (Weird!)

Example of a

metallic solid:

magnesium

sea of electrons model

cation “core”

e-

e-

e-^ e-

e-

e-

e-

e- e-

e-

Delocalized valence electrons (move around)

Why are metal solids malleable while

ionic solids are brittle?

Metallic solid

Ionic solid

Molecular Orbital Energy Levels Produced When Various Numbers of Atomic Orbitals Interact

Bonding in metals:

Band or Molecular Orbital (MO) Model

Two Types of Alloys

• Brass is a

substitutional

alloy.

• Steel is an

interstitial alloy.

Example of a

covalent solid:

quartz

The unhybridized p orbitals and π - system

in graphite

SiO 2 : quartz vs. glass

quartz (crystalline) glass (amorphous)

n-type semiconductor:

silicon crystal doped with arsenic

extra e- free to move

p-type semiconductor:

silicon crystal doped with boron

A missing electron → a positive “hole” that moves in the opposite direction to the electrons that move to fill it