metallic bonds

formation of metallic bonds

A metallic bond is the force of attraction between a positive metal ion and the valence electrons it shares with other ions of the metal. The positive ions form a lattice-like structure. You can see an example in Figure 7.13. (For an animated version, go to the URL below.) The ions are held together in the lattice by bonds with the valence electrons around them. These valence electrons include their own and those of other ions. Why do metallic bonds form? Recall that metals "want" to give up their valence electrons. This means that their valence electrons move freely. The electrons form a "sea" of negative charge surrounding the positive ions. MEDIA Click image to the left or use the URL below. URL:

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metallic bonds and the properties of metals

Because of their freely moving electrons, metals are good conductors of electricity. Metals also can be shaped without breaking. They are ductile (can be shaped into wires) and malleable (can be shaped into thin sheets). Metals have these properties because of the nature of their metallic bonds. A metallic lattice, like the one in Figure 7.13, may resemble a rigid ionic crystal. However, it is much more flexible. Look at Figure 7.14. It shows a blacksmith hammering a piece of red-hot iron in order to shape it. Why doesnt the iron shatter, as an ionic crystal would? The ions of the metal can move within the "sea" of electrons without breaking the metallic bonds that hold them together. The ions can shift closer together or farther apart. In this way, the metal can change shape without breaking. You can learn more about metallic bonds and the properties of metals at this URL: (6:12). MEDIA Click image to the left or use the URL below. URL:

alloys

Metals are useful for many purposes because of their unique properties. However, pure metals may be less useful than mixtures of metals. For example, iron is not as strong as steel, which is a mixture of iron and small amounts of carbon. Steel is so strong that it can hold up huge bridges, like the one Figure 7.15. Steel is also used to make skyscrapers, cargo ships, cars, and trains. Steel is an example of an alloy. An alloy is a mixture of a metal with one or more other elements. The other elements may be metals, nonmetals, or both. An alloy is a solid solution. It is formed by melting a metal and dissolving the other elements in it. The molten solution is then allowed to cool and harden. Several other examples of alloys and their uses are shown in Figure 7.16. You can learn about an amazing alloy called memory wire at the URL below. If you have braces on your teeth, you may even have this alloy in your mouth!

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instructional diagrams

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questions

Metallic bonds form because metals

-->  a. want to give up valence electrons.

b. always share valence electrons.

c. have many valence electrons.

d. always gain valence electrons.

Which statement about metallic bonds is true?

a. They form between metals and nonmetals.

b. They form between negative and positive ions.

-->  c. They form a lattice-like structure.

d. two of the above

Which statement is true about all metals?

a. They have one valence electron.

-->  b. They have freely moving electrons.

c. They have more electrons than protons.

d. They always gain electrons.

In metallic bonds, the force of attraction is between

a. positive and negative ions.

-->  b. ions and electrons.

c. two different metals.

d. neutrons and electrons.

Because of metallic bonds, metals

a. are good conductors of electricity.

b. can change shape without breaking.

c. are ductile and malleable.

-->  d. all of the above

Metals are used to make electric wires because metals

a. are ductile.

b. are malleable.

c. have freely moving electrons.

-->  d. two of the above

How does a metallic lattice differ from an ionic crystal?

a. A metallic lattice is less flexible.

-->  b. A metallic lattice can change shape without breaking.

c. A metallic lattice shatters when struck.

d. all of the above

An alloy is a

a. pure metal.

b. compound of two or more metals.

-->  c. solid solution.

d. mixture of nonmetals.

Metal ions are surrounded by a sea of

-->  a. electrons.

b. positive ions.

c. negative ions.

d. positive charges.

An alloy of iron and carbon is

a. more likely to rust than pure iron.

b. weaker than pure iron.

c. a mixture of two metals.

-->  d. known as steel.

The alloy that contains iron, carbon, nickel, and chromium is called

-->  a. stainless steel.

b. bronze.

c. brass.

d. gol

type of ion a metal forms

a. alloy

b. metallic bond

c. metal

-->  d. cation

e. iron

f. steel

g. metallic lattice

structure formed by metallic bonding

a. alloy

b. metallic bond

c. metal

d. cation

e. iron

f. steel

-->  g. metallic lattice

example of an alloy

a. alloy

b. metallic bond

c. metal

d. cation

e. iron

-->  f. steel

g. metallic lattice

any element that is a good conductor of electricity

a. alloy

b. metallic bond

-->  c. metal

d. cation

e. iron

f. steel

g. metallic lattice

A metallic bond may form between a metal and any other element.

a. true

-->  b. false

example of a metal

a. alloy

b. metallic bond

c. metal

d. cation

-->  e. iron

f. steel

g. metallic lattice

Metals can be shaped into thin sheets.

-->  a. true

b. false

mixture of a metal with one or more other elements

-->  a. alloy

b. metallic bond

c. metal

d. cation

e. iron

f. steel

g. metallic lattice

Metal ions are surrounded by a sea of positive charge.

a. true

-->  b. false

force of attraction between a metal ion and valence electrons it shares with other ions of the metal

a. alloy

-->  b. metallic bond

c. metal

d. cation

e. iron

f. steel

g. metallic lattice

Special bonds form in metals that do not form in other classes of elements.

-->  a. true

b. false

Bronze has been used for thousands of years.

-->  a. true

b. false

Brass is an alloy of iron and copper.

a. true

-->  b. false

A metallic lattice is more rigid than an ionic crystal.

a. true

-->  b. false

Metallic bonds explain some of the unique properties of metals.

-->  a. true

b. false

Metal ions form bonds with the valence electrons around them.

-->  a. true

b. false

Examples of metals include iron, zinc, and carbon.

a. true

-->  b. false

A metallic lattice is held together by ionic bonds.

a. true

-->  b. false

Iron is stronger than steel.

a. true

-->  b. false

Most metal objects are made of alloys.

-->  a. true

b. false

Bronze is a compound of copper and tin.

a. true

-->  b. false

Gold jewelry is usually made of pure gold.

a. true

-->  b. false

diagram questions

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