20.Metallic Bonding: Properties, Alloys & Pure Metals

Structure: Metals consist of a giant structure of atoms arranged in a regular pattern.
The Process: Metal atoms give up their outer shell electrons to a shared "pool."
Positive Ions & Delocalized Electrons: Because the atoms lose electrons, they become positive ions. The electrons are free to move throughout the structure and are called delocalized electrons.
The Bond: Metallic bonding is the strong electrostatic attraction between these positive metal ions and the sea of negative delocalized electrons. This attraction holds the regular structure together.

Strength & High Melting Points: The electrostatic forces are very strong, giving metals high strength and high melting/boiling points. Most are solid at room temperature.
Conductivity: Metals are excellent conductors of electricity and heat because the delocalized electrons are free to move and carry electrical current or thermal energy through the structure.
Malleability: Metals are malleable, meaning they can be bent or hammered into shapes (like thin sheets). This is possible because the atoms are arranged in regular layers that can slide over one another.

Pure Metals: Often too soft for many uses because their identical-sized atoms are in regular layers that slide easily.
Alloys: A mixture of two or more different elements (usually two metals, or a metal and a non-metal).
Why Alloys are Harder: Alloys use atoms of different sizes. This disrupts the regular layered structure of the metal, preventing the layers from sliding over each other.
Example (Steel): Pure iron is relatively soft. By adding a small amount of carbon (and sometimes other metals like chromium or manganese), it becomes steel, which is much harder and stronger, making it suitable for cars and planes.