unit 3 lesson 4 ionic, covalent, and metallic bonding copyright © houghton mifflin harcourt...

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

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Page 1: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Copyright © Houghton Mifflin Harcourt Publishing Company

Page 2: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

Opposites Attract

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What is an ion?

• An atom has a neutral charge because it has an equal number of electrons and protons.

• An ion is a particle with a positive or negative charge.

• An ion forms when an atom gains or loses electrons from its outer, or valence, shell.

Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 3: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

How does an ionic bond form?

• An ionic bond is a force that brings oppositely charged ions together.

• Ionic bonds form when electrons are transferred from a metal atom to a nonmetal atom.

• In the process of ionic bonding, valence electrons move from the outer shell of the metal atom to the outer shell of the nonmetal atom.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 4: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

How does an ionic bond form?

• How are the sodium and chlorine atoms held together in the compound sodium chloride?

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 5: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most ionic compounds share?• When ions bond, they form a repeating three-

dimensional pattern called a crystal lattice.

• Each ion has many oppositely charged ions around it, and every ion is held firmly in place with strong bonds.

• It takes a lot of energy to separate these ions from one another. So most ionic compounds have high melting and boiling points.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 6: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most ionic compounds share?• Sodium chloride consists of sodium and chloride

ions held together in a crystal lattice structure.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 7: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most ionic compounds share?• The crystals of ionic compounds are hard and

brittle.

• Striking a crystal of an ionic compound with a hammer will likely shatter the crystals in many places.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 8: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most ionic compounds share?• Solid ionic compounds are poor conductors of

electric current, because the ions are held tightly in place.

• Melting an ionic solid, however, allows the individual ions to move around. Melted ionic compounds can conduct an electric current.

• Ionic compounds dissolved in water can also conduct an electric current.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 9: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most ionic compounds share?• Solubility is the ability to dissolve in liquid. Most

ionic compounds dissolve in water.

• When salt is added to water, water molecules attract the positive and negative salt ions.

• Water molecules surround each ion, and move the ions apart from each other. The separated ions dissolve in water.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 10: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

Let’s Share!

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What is a covalent bond?

• A covalent bond forms when atoms share one or more pairs of electrons.

• When two nonmetal atoms bond, a large amount of energy is needed for either atom to lose an electron. So they bond by sharing electrons.

• In a covalent bond, the shared electrons fill empty spaces in the outermost electron shell of each atom.

Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 11: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What is a molecule?

• Substances that have covalent bonds are made of individual particles called molecules.

• A molecule is a group of atoms held together by chemical bonds.

• A molecule is the smallest unit of a compound that can be identified as that compound.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 12: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What is a molecule?

• In a water molecule, two hydrogen atoms form covalent bonds with a central oxygen atom.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 13: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most covalent compounds share?• Some covalent compounds dissolve in water.

Other covalent compounds do not.

• Wax molecules have a stronger attraction to other wax molecules than they have to water molecules. This is why wax does not dissolve in water.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 14: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most covalent compounds share?• When a covalent compound melts or boils, the

covalent bonds holding the molecules together do not break as ionic bonds in an ionic compound do.

• Instead, one molecule separates from another.

• Because molecules separate easily from other molecules, they tend to have lower melting and boiling points than ionic compounds.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 15: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most covalent compounds share?• Most covalent compounds are poor conductors of

electric current in both solid and liquid form.

• Unlike ions, which are charged, molecules are neutral.

• So, even in a liquid in which molecules can move around, the compound cannot conduct electric current.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 16: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

Free to Move

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How does a metallic bond form?

• A metallic bond forms between metal atoms when their outermost energy levels overlap.

• Metallic bonding is weak compared to ionic or covalent bonding.

• You can think of a metal as being made up of positive metal ions with enough valence electrons “swimming” around to hold the ions together.

Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 17: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

How does a metallic bond form?

• Copper metal is held together by metallic bonding, in which electrons flow around copper ions.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 18: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most metallic compounds share?• Because the electrons in a metal can move freely,

most metals are good conductors of electric current.

• When you turn on a lamp, valence electrons move through the copper wire that connects the light bulb to the electrical outlet.

• The valence electrons in the copper atoms are free to move because they are not connected to any one atom.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding

Page 19: Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding Copyright © Houghton Mifflin Harcourt Publishing Company

What properties do most metallic compounds share?• Due to their free-moving electrons, metals have

two properties that allow them to be reshaped.

• Malleability is the ability to be hammered into sheets.

• Ductility is the ability to be formed into long, thin wires.

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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding