Chapter 13
Chemical Bonding
Preview
Section 1 Electrons and Chemical Bonding
Section 2 Ionic Bonds
Section 3 Covalent and Metallic Bonds
Concept Mapping
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Chapter 13
Section 1 Electrons and
Chemical Bonding
Bellringer
Look at these chemical formulas:
C6H1206
C2H5OH
C6H8O6
C6H8O7
Identify the elements in these compounds and predict
whether the compounds are similar to each other.
Explain your reasoning.
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Chapter 13
Section 1 Electrons and
Chemical Bonding
Objectives
• Describe chemical bonding.
• Identify the number of valence electrons in an atom.
• Predict whether an atom is likely to form bonds.
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Chapter 13
Section 1 Electrons and
Chemical Bonding
Combining Atoms Through
Chemical Bonding
• Chemical bonding is the joining of atoms to form
new substances.
• An interaction that holds two atoms together is called
a chemical bond. When chemical bonds form,
electrons are shared, gained, or lost.
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Chapter 13
Section 1 Electrons and
Chemical Bonding
Combining Atoms Through
Chemical Bonding, continued
• Discussing Bonding Using Theories and Models
We cannot see atoms and chemical bonds with the
unaided eye.
• So, the use of models helps people discuss the
theory of how and why atoms form bonds.
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Chapter 13
Section 1 Electrons and
Chemical Bonding
Electron Number and Organization
• The number of electrons in an atom can be
determined from the atomic number of the element.
• Electrons in an atom are organized in energy levels.
• The next slide shows a model of the arrangement of
electron in an atom. This model and models like it are
useful for counting electrons, but do not show the true
structure of an atom.
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Chapter 13
Section 1 Electrons and
Chemical Bonding
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Chapter 13
Section 1 Electrons and
Chemical Bonding
Electron Number and Organization,
continued
• Outer-Level Electrons and Bonding Most atoms
form bond using only its valence electrons, the
electrons in an atom’s outermost energy level.
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Chapter 13
Section 1 Electrons and
Chemical Bonding
Electron Number and Organization,
continued
• Valence Electrons and the Periodic Table You can
use the periodic table to determine the number of
valence electrons for atoms of some elements, as
shown on the next slide.
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Chapter 13
Section 1 Electrons and
Chemical Bonding
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Chapter 13
Section 1 Electrons and
Chemical Bonding
To Bond or Not to Bond
• The number of electrons in the outermost energy
level of an atom determine whether an atom will form
bonds.
• Atoms that have 8 electrons in their outermost energy
level do not usually form bonds. The outermost energy
level is considered to be full if it contains 8 electrons.
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Chapter 13
Section 1 Electrons and
Chemical Bonding
To Bond or Not to Bond, continued
• Filling the Outermost Level An atom that has fewer
than 8 valence electrons is more likely to form bonds
than at atom that has 8 valence electrons is. Atoms
bond by gaining, losing, or sharing electrons to have a
filled outermost energy level.
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Chapter 13
Section 1 Electrons and
Chemical Bonding
To Bond or Not to Bond, continued
• Is Two Electrons a Full Set? Not all atoms need 8
valence electrons to have a filled outermost energy
level. Helium atoms need only 2 valence electrons
because the outermost level is the first energy level.
• Atoms of hydrogen and lithium form bonds by
gaining, losing, or sharing electrons to achieve 2
electrons in the first energy level.
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Chapter 13
Section 2 Ionic Bonds
Bellringer
Salts are ionic compounds. Brainstorm uses for salts,
things that contain salts, and words and phrases
containing the term salt.
Write your responses in your science journal.
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Chapter 13
Section 2 Ionic Bonds
Objectives
• Explain how ionic bonds form.
• Describe how positive ions form.
• Describe how negative ions form.
• Explain why ionic compounds are neutral.
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Chapter 13
Section 2 Ionic Bonds
Forming Ionic Bonds
• An ionic bond is a bond that forms when electrons
are transferred from one atom to another atom.
• Charged Particles An atom is neutral because the
number of electrons in an atom equals the number of
protons. So, the charges cancel each other out.
• But when an atom gains or loses electrons, it
becomes a charged particle called an ion.
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Chapter 13
Section 2 Ionic Bonds
Forming Positive Ions
• Metal Atoms and the Loss of Electrons Atoms of
most metals have few valence electrons and tend to
lose these valence electrons and form positive ions.
• The Energy Needed to Lose Electrons Energy is
needed to pull electrons away from atoms. The energy
needed comes from the formation of negative ions.
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Chapter 13
Section 2 Ionic Bonds
Forming Negative Ions
• Nonmetal Atoms Gain Electrons The outer energy
level of nonmetal atoms is almost full. So, nonmetal
atoms tend to gain electrons and become negative ions.
• The Energy of Gaining Electrons Energy is given off
when nonmetals gain electrons. An ionic bond will form
between a metal and a nonmetal if the nonmetal
releases more energy than is needed to take electrons
from the metal.
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Chapter 13
Section 2 Ionic Bonds
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Chapter 13
Section 2 Ionic Bonds
Ionic Compounds
• When ionic bonds form, the number of electrons lost
by the metal atoms equals the number gained by the
nonmetal atoms.
• The ions that bond are charged, but the compound
formed is neutral because the charges of the ions
cancel each other.
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Chapter 13
Section 2 Ionic Bonds
Ionic Compounds, continued
• When ions bond, they form a repeating threedimensional pattern called a crystal lattice, such as
the one shown below.
• Properties of ionic
compounds include
brittleness, high melting
points, and high boiling
points.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Bellringer
Take a minute or two to brainstorm a list of things
made of metal. Then, use your list to describe three
properties of metals.
Write your responses in your science journal.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Objectives
• Explain how covalent bonds form.
• Describe molecules.
• Explain how metallic bonds form.
• Describe the properties of metals.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Covalent Bonds
• A covalent bond forms when atoms share one or
more pairs of electrons.
• Substances that have covalent bonds tend to have
low melting and boiling points and are brittle in the
solid state.
• Covalent bonds usually form between atoms of
nonmetals, such as the atoms shown on the next slide.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Covalent Bonds, continued
• Covalent Bonds and Molecules Substances
containing covalent bonds consist of particles called
molecules. A molecule usually consists of two or more
atoms joined in a definite ratio.
• The models on the next slide show two ways to
represent the covalent bonds in a water molecule.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Covalent Bonds, continued
• One way to represent atoms and molecules is to use
electron-dot diagrams. An electron-dot diagram shows
only the valence electrons in an atom.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Covalent Compounds and Molecules
• A molecule is the smallest particle into which a
covalently bonded compound can be divided and still
be the same compound.
• The Simplest Molecules are made up of two
bonded atoms. Molecules made up of two atoms of the
same element are called diatomic molecules.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Covalent Compounds and Molecules,
continued
• More-Complex Molecules Carbon atoms are the
basis of many complex molecules.
• Each carbon atom can form
four covalent bonds. These
bonds can be with atoms of other
elements or with other carbon
atoms, as shown at right.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Metallic Bonds
• A metallic bond is a bond formed by the attraction
between positively charged metal ions and the
electrons in the metal.
• Movement of Electrons Throughout a Metal
Bonding in metals is a result of the metal atoms being
so close to one another that their outermost energy
levels overlap. This overlapping allows valence
electrons to move throughout the metal.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Metallic Bonding
Click below to watch the Visual Concept.
Visual Concept
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Properties of Metals
• Conducting Electric Current Metallic bonding
allows metals to conduct electric current.
• Electric current is conducted when valence
electrons move within a metal. These electrons are
free to move because the electrons are not
connected to any one atom.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Properties of Metals, continued
• Reshaping Metals Because the electrons swim
freely around the metal ions, atoms in metals can be
rearranged. The properties of ductility and malleability
describe a metal’s ability to be reshaped.
• Ductility is the ability to be draw in to wires.
• Malleability is the ability to be hammered into sheets.
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Chapter 13
Section 3 Covalent
and Metallic Bonds
Properties of Metals, continued
• Bending Without Breaking When a piece of metal
is bent, some of the metal ions are forced closer
together.
• But the metal does not break because the positive
metal ions are always surround by and attracted to the
electrons in the metal.
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Chapter 13
Chemical Bonding
Concept Mapping
Use the terms below to complete the Concept
Mapping on the next slide.
covalent bonds
ions
molecules
electrons
metallic bonds
chemical bonds
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Chapter 13
Chemical Bonding
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Chapter 13
Chemical Bonding
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