Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding
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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding
Opposites Attract
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.
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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding
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
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
What properties do most ionic
compounds share?
• When ions bond, they form a repeating threedimensional 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
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
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
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
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
Let’s Share!
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.
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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding
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
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
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
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
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
Free to Move
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.
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Unit 3 Lesson 4 Ionic, Covalent, and Metallic Bonding
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
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
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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