1. Solids  Solids retain their shapes because they have rigid crystal structures.  Based on the attractive forces that hold tem together or on the arrangement of the atoms in the crystals themselves.

2. Solids  Crystal Types Based on Attractive Forces  Metallic crystals  Ionic crystals  Molecular crystals  Network (covalent) crystals  Amorphous (noncrystalline) substances

3. Solids  Metallic Crystals  All metals in the periodic table are solids at 25°C, except mercury.  A rigid structure of metal nuclei and inner electrons, valence electrons are very mobile, moving freely from atom to atom.  Mobile e - bond atoms together with widely varying degrees of force  Fe, Cr, Co, Au, Pt, & Cu have MP above 1000°C.  Hg & Ga melt at or below room temperature Bi

4. Solids  Metallic crystals  Mobile valence e - explain the ability of metals to conduct heat & electricity  Interaction of light with mobile valence e - is responsible for a metal’s luster  Some metals (Pb, Au, Na, & K) are soft & can be cut with a knife  Others (Sn & Zn) are brittle  Most metals are malleable & ductile  These properties are due to crystal structure- allow movement of atoms without a major disruption in the crystals Malleable Ductile