1. 11.4 NOTES Solids

2. B. Solids
1. Density of solids
- particles are more closely packed than liquids, the result is most solids are more dense than the liquid (exception - water);
- ordinary amounts of pressure will not change the volume of a solid (noncompressible)
- porous materials like a sponge seem compressible, but compression does not reduce the volume of the solid portion significantly, it reduces the volume of the pores in the solid)

3. 2. Crystalline solids
- a solid whose atoms, ions, or molecules are arranged in an orderly, geometric, 3-D structure
- individual pieces of crystalline solids are known as crystals;
- examples – any ionic compound

4. 3. Amorphous solids
- particles are not arranged in a regular, repeating pattern, DO NOT contain crystals
- examples – glass, wax, rubber, and many plastics;

5. Solids are classified into 4 general types:
Molecular – H2O, I2 – discrete (individual) molecules
Network covalent – diamonds, SiO2, continuous network of atoms connected by covalent bonds
Ionic – NaCl, KBr – made of cations and anions in a lattice
Metallic – Zn, Cu, Na – cations surrounded by a sea of mobile electrons

6. 4. Molecular Solids all 3 intermolecular forces are available; molecules share e-
a. Nonconductors when pure. Very polar ones conduct in water (HCl, for example)
b. Generally insoluble in water, but soluble in nonpolar solvents. A few polar molecules do dissolve in water – alcohols for example (CH3OH or CH3CH2OH).
c. Volatile due to weak intermolecular forces
d. Low melting and boiling points. Upper limit for MP is 300°C. The forces between the molecules are weak, but the covalent bonds within the molecules stay intact when substance is melted or boiled.
e. Examples: most not solids at room temp; (water), sugar is a solid b/c large molar mass (many dispersion forces combine to hold the molecule together); I2, H2O, NH3, CO2, C12H22O11(Sucrose)

7. Covalent network solids atoms that form multiple covalent bonds; millions of atoms; tremendously strong;
a. Always solids – extremely high melting, often > 1000°C. To melt network solids, strong covalent bonds must be broken – structure is destroyed.
b. Insoluble in all solvents
c. Poor conductors, except for graphite
d. All network solids: C (diamond and graphite), Si, Ge, P (red), SiC, BN, SiO2
Compare diamond and graphite in terms of structure:

9. Ionic solids (salts) type of ions and the ratio of ions determine the structure of the lattice and the shape of the crystal
a. Nonvolatile and high melting points (600 – 2000°C) due to network of attractions that extend throughout an ionic crystal; no dispersion forces
b. Do not conduct as solids, do conduct when melted or dissolved in water
c. Many are soluble in water. None are soluble in nonpolar solvents (CCl4, benzene, hexane)
d. Examples: NaCl, MgF2, KBr, CaCO3

10. 7. Metallic solids
Composed of positive ions surrounded by a sea of valence electrons (delocalized electrons). The model explains why metals are:
1 – good conductors of heat
2 – good conductors of electricity
3 – shiny
4 – malleable
5 – ductile
electrons are held very loosely in the “sea”;

11. Strength of a metallic bond depends on charge(or number of valence electrons):
Na+ m.p. 98°C
Mg+2 m.p. 650°C
Cr, with 6 valence electrons, has a m.p. of 1890°C
Give the general relationship:
increase # of valence electrons, increases the melting point of the metal
range of m.p.: Hg = -40°C, W = 3422 °C
Strength of metallic bond also depends on the size of the ion: the larger the ion, the weaker the bond; explains why cesium compounds have low melting points (Cs is so large)

12. Properties of metals:
a. Nonvolatile (except Hg)
b. Insoluble in H2O and common solvents. Active metals do react with water. Group 1A and heavy 2A will react with water to form H2 and metallic hydroxide solutions;
c. Liquid Hg dissolves other metals to form alloys called amalgams
Ag-Sn-Hg amalgam is used for dental fillings
d. Soft to very hard, malleable, ductile
examples – Na, Fe, Mg, Ca, Ag, Au – all metallic elements

13. Classifying Solids –
a. Does the solid contain a metal? Yes – go to A; No – go to B
A. Does it contain an anion? Yes – the solid is an ionic solid; No – the solid is a metallic solid.
B. Is it 1 of the 7? Yes – the solid is a network; No – the solid is a molecular solid

14. Classify the following solids –
a) SiH b) NaCl c) sugar, C6H12O d) Cu
e) SiO f) K g) BN h) MgO

15. Video Links –
(Solids and Liquids)
(Ionic Solids)
(Metallic Solids)
(Covalent Network Solids)
(Molecular Solids)