The Nature of Solids

General Properties Orderly… Repeating… arrangement of particles Fixed location geometric

Structure Most solids are crystalline Form a Crystal Lattice Orderly, repeating, 3-D pattern of particles Unit Cell Smallest group within a lattice that retains the geometric shape of the crystal.

Cubic Crystal Lattices

Allotropes Some solid substances can exist in more than one form. Diamond… Graphite… Coal

Crystal Structure of Diamond The ball-and-stick diagram shows the crystal structure of diamond, a covalent network solid. Each corner or intersection of lines represents a carbon atom. Notice the tetrahedral arrangement at each carbon atom.

Graphite Structure The ball-and-stick diagram of graphite shows the that the carbon atoms form a network of hexagonal rings within each plane. The planes are stacked in layers that can slide over one another.

Buckeyballs (Fullerenes) C60 The ball-and-stick diagram shows carbon atoms in a spherically shaped arrangement like the surface of a soccer ball with 60 carbon atoms in interconnected 5- and 6-member rings forming buckminsterfullerenes, or Buckyballs. They were first prepared in 1985. Buckminsterfullerene molecule

Nanotube Cable The diagram shows a ball-and-stick model of a nanotube with carbon atoms in six-membered rings bonded in honeycomb-shaped, cylindrical structures. Nanotubes having strands narrower than a human hair and 10 times stronger than steel were first prepared in 1997.

Definition Allotropes are two or more different molecular forms of the same element in the same physical state but different properties. Only a few elements have allotropes: Carbon, Phosphorous, Sulfur, and Oxygen Metalloids : Boron and Antimony

Non-Crystalline Solids A amorphous solid lacks an ordered internal structure. Atoms are randomly arranged. Examples include: Rubber, plastic, and asphalt Coal and Glasses

More on Glasses A glass is a transparent fusion product of inorganic substances that have cooled to a rigid state without crystallizing. Glasses do NOT melt at a definite temperature; instead they gradually soften when heated. Shatter → fragments have irregular angles and jagged edges

Molecular Structure of a Crystal

Molecular Structure of a Glass