Chemical Bonding New

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Chapter 12 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 12

Bellringer

The following are some very common chemical

formulas.

C6H12O6 C2H5OHC6H8O6 C6H8O7

Identify the elements in these compounds and predict

whether the compounds are similar to each other and

why.

Record your answers in yourscience journal.

Section1 Electrons and Chemical Bonding


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Chapter 12

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 12

Combining Atoms ThroughChemical Bonding

Chemical bonding is the joining of atoms to form

new substances.

An interaction that holds two atoms together is called

achemical bond. When chemical bonds form,

electrons are shared, gained, or lost.



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Chapter 12

Combining Atoms ThroughChemical 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 12

Electron Number and OrganizationThe 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 truestructure of an atom.



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Chapter 12 Section1 Electrons and Chemical Bonding


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Chapter 12

Electron Number and Organization,continued

Outer-Level Electrons and Bonding Most atoms

form bonds using only itsvalence electrons,the

electrons in an atoms outermost energy level.



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Chapter 12

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, asshown on the next slide.



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Chapter 12 Section1 Electrons and Chemical Bonding


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Chapter 12

To Bond or Not to BondThe 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 12

To Bond or Not to Bond, continued Filling the Outermost LevelAn atom that has fewer

than 8 valence electrons is more likely to form bonds

than an atom that has 8 valence electrons is. Atoms

bond by gaining, losing, or sharing electrons to have afilled outermost energy level.



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Chapter 12

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 12 Section2 Ionic Bonds

Bellringer

Historically, salt has had many uses beyond just a

spice you put in your soup. Salts are ionic

compounds. Brainstorm some uses for salts, thingsthat contain salts, or words and phrases containing

the term salt. Where do you think salt comes from?

Write your answers in yourscience journal.


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Chapter 12

Objectives

Explain how ionic bonds form.

Describe how positive ions form.

Describe how negative ions form.

Explain why ionic compounds are neutral.

Section2 Ionic Bonds


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Chapter 12

Forming Ionic BondsAnionic bondis a bond that forms when electrons

are transferred from one atom to another atom.

Charged ParticlesAn atom is neutral because thenumber 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, itbecomes a charged particle called anion.



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Chapter 12

Forming Positive IonsMetal Atoms and the Loss of ElectronsAtoms 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 12

Forming Negative IonsNonmetal 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 electronsfrom the metal.



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Chapter 12 Section2 Ionic Bonds


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Chapter 12

Ionic CompoundsWhen 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 12

Ionic Compounds, continuedWhen ions bond, they form a repeating three-

dimensional pattern called acrystal lattice,such as

the one shown below.

Properties of ionic

compounds include

brittleness, high melting

points, high boiling

points, and increase

electrical conductivity

when dissolved in water

solutions.



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Chapter 12

Bellringer

Brainstorm a list of things made of metal. Record

your list in yourscience journal.Describe three

properties of metals based on your list. The useof metal has been key to human technological

development. List the types of metal that you use in

your everyday life and how you use them. What are

the properties of metal that make it useful? What

are some of the drawbacks of using metal?

Section3 Covalent and Metallic Bonds


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Chapter 12

Objectives

Explain how covalent bonds form.

Describe molecules.

Explain how metallic bonds form.

Describe the properties of metals.



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Chapter 12

Covalent BondsAcovalent bondforms when atoms share one or

more pairs of electrons.

Substances that have covalent bonds tend to havelow melting and boiling points and are brittle in the

solid state.

Covalent bonds usually form between atoms ofnonmetals, such as the atoms shown on the next slide.



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Chapter 12 Section3 Covalent and Metallic Bonds


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Chapter 12

Covalent Bonds, continued Covalent Bonds and Molecules Substances

containing covalent bonds consist of particles called

molecules. Amoleculeusually 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 12 Section3 Covalent and Metallic Bonds


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Chapter 12

Covalent Bonds, continuedOne 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 12

Covalent Compounds and MoleculesA molecule is the smallest particle into which a

covalently bonded compound can be divided and still

be the same compound.

The Simplest Moleculesare 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 12

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 12

Metallic BondsAmetallic bondis 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 valenceelectrons to move throughout the metal.



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Chapter 12

Metallic Bonding

Click below to watch the Visual Concept.

Visual Concept

http://d/PowerPoint/ch_ppts/ch12/75483.htmlhttp://d/PowerPoint/ch_ppts/ch12/75483.html


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Chapter 12

Properties of MetalsConducting Electric Current Metallic bonding

allows metals to conduct electric current.

Electric current is conducted when valenceelectrons 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 12

Properties of Metals, continuedReshaping Metals Because the electrons swim

freely around the metal ions, atoms in metals can be

rearranged. The properties ofductilityand malleability

describe a metals 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 12

Properties of Metals, continuedBending 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.


C


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Use the terms below to complete the concept map

on the next slide.

covalent bonds electronsions metallic bonds

molecules chemical bonds

Concept Mapping

Ch t 12


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Ch t 12


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