Study Guide: Metallic Bonds and Properties of Metals

Section 7.4 Metallic Bonds and the Properties of Metals

Overview

• The section discusses metallic bonds and the characteristics of metals.
• It also provides questions for assessment based on a model of metallic bonding as depicted in a diagram.

Metallic Bonding

• Definition of Metallic Bonds: Metallic bonding occurs when metal atoms share their delocalized electrons, allowing for a structure that can conduct electricity and heat.
• Diagram Explanation: A diagram typically illustrates the arrangement of metal cations surrounded by a sea of delocalized electrons, which is a fundamental characteristic of metallic bonding.

Key Questions about Metallic Bonding

1. What is the name of the model of metallic bonding that is illustrated?

   • The model is referred to as the "Sea of Electrons" model. This model shows that electrons are not localized to individual atoms but are instead spread out over many atoms.

2. Why are the electrons in a metallic solid described as delocalized?

   • Electrons are termed delocalized because they are not bound to any single atom and can move freely throughout the metallic structure. This mobility contributes to the good electrical and thermal conductivity of metals.

3. Which electrons from the metal make up the delocalized electrons?

   • The delocalized electrons primarily originate from the valence shell electrons of the metal atoms, particularly those that are in the outermost shell and are involved in bonding.

4. Are the metal atoms that are shown cations or anions? How can you tell?

   • The metal atoms depicted in the model are cations. This conclusion is derived from the fact that metals lose their valence electrons to achieve stability, resulting in a positively charged state.

5. How do the metallic ions differ from the ions that exist in ionic solids?

   • Metallic ions in a metallic bond are surrounded by a sea of electrons, whereas the ions in ionic solids are held together by ionic bonds (the electrostatic attraction between oppositely charged ions). Additionally, in metallic bonds, the cations are in a communal electron cloud, while ionic solids exist as discrete pairs of anions and cations.

6. Explain what holds the metal atoms together in the solid.

   • The metal atoms in a metallic solid are held together by the metallic bonds formed between the cations and the delocalized electrons. The attraction between the positively charged metallic ions (cations) and the negatively charged sea of electrons results in a stable structure.

Properties of Metals

• Metals exhibit unique physical and chemical properties such as:
  • High electrical conductivity
  • High thermal conductivity
  • Malleability (ability to be hammered into thin sheets)
  • Ductility (ability to be drawn into wires)
  • Lustrous appearance
  • High melting and boiling points

Assessment of Properties

• For each property, write "yes" if the property is applicable to metals:
  • Conductivity: yes
  • Malleability: yes
  • Ductility: yes
  • Luster: yes
  • High melting points: yes

Note: Each property of metals is a consequence of the metallic bonding model and the arrangements of the delocalized electrons.