Section 8.4 Metallic Bonds and Properties of Metals

1. Section 8.4 Metallic Bonds and Properties of Metals Objectives: Describe a metallic bond Explain the physical properties of metals in terms of metallic bonds Define and describe alloys

2. Metallic Bonds Electron Sea Model � Proposes that all metal atoms in a metallic solid contribute their valence electrons form a sea of electrons Electrons in the outer level are free to move in any direction Delocalized electrons- electrons in the outer energy levels that are free to move Metallic Bond- attraction of a metallic cation for delocalized electrons

3. Properties of Metals Physical properties can be explained by metallic bonding Properties determine the strength of the bonds

4. Examples of Properties Melting point vary greatly Mercury liquid at room temperature Tungsten melts at 3244degrees Celsius Metals are Malleable and Ductile During these processes particles can be pushed and pulled very easily Luster � Metals absorb and release photons making metals have a high luster

5. Examples of Properties Hardness- Transition metals have 2 outer electrons Alkali metals have 1 outer electron The more delocalized electrons the increases the strength and hardness

6. Metal Alloys Alloy- mixture of elements that have metallic properties 2 types of alloys Substitutional alloy- has atoms of the original metallic solid replaced by other metal atoms of similar size Example: Sterling silver Interstitial alloy- formed when small holes in a metallic crystal are filled with smaller atoms Example: Carbon steel