Chapter 13 The Chemistry of Solids Types of Solids Metals Network Ionic Molecular Amorphous

Chapter 13 The Chemistry of Solids Types of SolidsExamples MetalsCopper NetworkQuartz IonicNaCl MolecularCO 2, CI 4 Amorphousglass, polyethylene

Types of SolidsCharacteristics MetalsCopper - malleable NetworkQuartz – non-malleable Molecularsulfur (S8) CO 2, CI 4 – low melting pt Ionic &muscovite– cleaves easy Network, Layered structure

The Chemistry of Solids What characteristic do these solids share?

The Chemistry of Solids What characteristic do these solids share? Repeating Structural Pattern other terms : Lattice Array Crystal Structure or Crystal Lattice

The Chemistry of Solids UNIT CELL is the smallest piece of the pattern that generates the lattice. UNIT CELL is a conventional choice. May have several unit cells possible, Different in shape and/or size. Translation directions

The Chemistry of Solids UNIT CELL is a conventional choice. May have several unit cells possible, Different in shape and/or size.

Three Types of Cubic Unit Cells a c b Simple Cubic Body Centered Cubic Face Centered Cubic

These Three Cubic Unit Cells are Structures of most Metallic Elements (also hexagonal, hcp, to be seen Friday) Cu, Ag, Au are all fcc Cr, Mo, W are all bcc Only Po is simple cubic ( rare— why? ) Simple Cubic Body Centered Cubic Face Centered Cubic

One result of a metal’s “choice” to adopt a cubic, bcc or fcc lattice are metal properties Simple CubicBody Centered CubicFace Centered Cubic

Packing a Square Lattice: Makes a simple cubic cell

Can you pack spheres more densely? The Rhomb is the Unit Cell Shape of Hexagonal Lattices

Closest Packing: hexagonal layers build up 3D solid

Find the triangular gaps in the Pink layer

Note how layers “sit” on top of each other: The Cyan layer covers the “up” triangles of the Pink layer The Yellow layer covers the “down” triangles of the Pink layer

This packing sequence is A B C A B C, Where B and C cover different “holes” in A B C A B C A

B C A B C A Packing direction ACBACBAACBACBA ccp Cubic Closest Packing: A B C A B C … Packing direction

CCP viewed unit cell; LOOK! It’s face centered cubic!!! CCP = FCC!! ….mmmMMM CCP viewed as packing layers A B C C B A

Effect of added atoms and grains on metal structure. Smaller atom like C in iron Larger atom like P in iron Second crystal phases precipitated Defects and grain boundaries “pin” structure. All these inhibit sliding planes and harden the metal.

Defects in metal structure

From Metals to Ionic Solids Will ionic solids pack exactly like metallic solids?

From Metals to Ionic Solids Build up Ionic Solids conceptually like this: assume Anions are larger than Cations, r- > r+ pack the Anions into a cubic lattice: ccp, simple or bcc add Cations to the interstitial spaces (“Mind the gap!”) 2 x r- r- + r+

The Simplest Ionic Solid is CsCl, simple cubic Start with simple cubic Unit cell of Cl- ions Then add one Cs+ in center Z = C. N. (Cs) = How to draw this

How to make NaCl: start with fcc unit cell of Cl- ions

Add Na+ in between

Add Na+ in between, everywhere

Z = C. N. (Na) =