Chemistry / Unit 4: Chemical Bonding
4.6 Metallic Bonds and Types of Solids
Notes
In a metallic bond, metal atoms share a "sea of electrons" that move freely among positive metal ions.
- Free electrons explain why metals conduct electricity and heat, are shiny, and are malleable (hammered into sheets) and ductile (drawn into wires): layers slide without breaking bonds.
- An alloy is a mixture of metals (brass = copper + zinc; steel = iron + carbon).
| Solid type | Particles | Properties | Example |
|---|---|---|---|
| ionic | ions | high melting point, brittle | NaCl |
| molecular | molecules | low melting point, soft | ice, sugar |
| network covalent | atoms in a covalent web | very high melting point, very hard | diamond, $\text{SiO}_2$ |
| metallic | metal ions in electron sea | conductive, malleable | copper |
Practice
Why can copper be drawn into wires?
The delocalized electrons hold the metal together even as layers of ions shift.
A solid melts at 3550 °C, is extremely hard, and does not conduct electricity. It is most likely:
Very high melting points and great hardness with no conductivity fit a covalent network like diamond.
Which describes an alloy?
Alloys are mixtures, like brass (copper and zinc) or steel (iron and carbon).
Ready for more? Take the Unit 4 test.