Metallic Bonding

Jean Brainard, Ph.D.

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Printed: August 25, 2016 www.ck12.org Chapter 1. Metallic Bonding

CHAPTER 1 Metallic Bonding

• Describe metallic bonds. • Explain how metallic bonds inﬂuence the properties of metals.

The thick, rigid trunk of the oak tree on the left might crack and break in a strong wind. The slim, ﬂexible trunk of the willow tree on the right might bend without breaking. In one way, metals are like willow trees. They can bend without breaking. That’s because metals form special bonds called metallic bonds.

What Are Metallic Bonds?

Metallic bonds are forces of attraction between positive metal ions and the valence electrons that are constantly moving around them (see the Figure 1.1). The valence electrons include their own and those of other, nearby ions of the same metal. The valence electrons of metals move freely in this way because metals have relatively low electronegativity, or attraction to electrons. The positive metal ions form a lattice-like structure held together by all the metallic bonds.

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Q: Why do metallic bonds form only in elements that are metals? Why don’t similar bonds form in elements that are nonmetals? A: Metal atoms readily give up valence electrons and become positive ions whenever they form bonds. When nonmetals bond together, the atoms share valence electrons and do not become ions. For example, when oxygen atoms bond together they form oxygen molecules in which two oxygen atoms share two pairs of valence electrons equally, so neither atom becomes charged.

Metallic Bonds and the Properties of Metals

The valence electrons surrounding metal ions are constantly moving. This makes metals good conductors of electricity. The lattice-like structure of metal ions is strong but quite ﬂexible. This allows metals to bend without breaking. Metals are both ductile (can be shaped into wires) and malleable (can be shaped into thin sheets).

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FIGURE 1.1 Metallic bonds.

Q: Look at the metalworker in the Figure 1.2. He’s hammering a piece of hot iron in order to shape it. Why doesn’t the iron crack when he hits it? A: The iron ions can move within the “sea” of electrons around them. They can shift a little closer together or farther apart without breaking the metallic bonds between them. Therefore, the metal can bend rather than crack when the hammer hits it.

FIGURE 1.2 Metal worker shaping iron metal.

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Summary

• Metallic bonds are the force of attraction between positive metal ions and the valence electrons that are constantly moving around them. The ions form a lattice-like structure held together by the metallic bonds. • Metallic bonds explain why metals can conduct electricity and bend without breaking.

Review

1. What are metallic bonds? 2. How do metallic bonds relate to the properties of metals? 3. The iron in the metal working picture above (Figure 1.2) is red hot. Infer why the metalworker heats the iron when he shapes it.

Explore More

Watch the video about metallic bonds at the following URL, and then answer the questions below.

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1. What is electricity? Why can metals conduct electricity? 2. What can metals conduct besides electricity? 3. How could you use an empty pop can to demonstrate that metals can bend without breaking?

References

1. Christopher Auyeung. Illustration of metallic bonds . CC BY-NC 3.0 2. Derek Key. Metal worker shaping iron on an anvil . CC BY 2.0