M A
1 4 : 0 5 : 1 1
0 1 / 4 2 /
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/24/10 11:50:41 AM You will also learn how to write You Read the two statements below and decide below statements Read the two chemically stable than they would be chemically stable than they would as individual atoms. easily in water dissolve substances Many molecule ends of a water because opposite charges. opposite have The atoms in a water molecule are more more molecule are in a water atoms The 4. 3. Chemical bonds join atoms together. Recall that a chemical Chemical bonds join atoms together. Have you ever baked cupcakes? The ingredients in the Have you ever baked cupcakes? In some ways, compounds are like the cupcakes. Recall Before Statement After What do you think? do you What column A in the Before an Place with them. or disagree agree whether you read you’ve After disagree. or a D if you with the statement agree if you mind. changed your have see if you to statements the this lesson, reread bond is a force that holds atoms together in a compound. bond is a force this lesson, you will learn how atoms can form bonds by In sharing valence electrons. read a chemical formula. and original ingredients. compound is a substance made up of two or more that a different elements. Just as cupcakes are different from their ingredients, compounds are different from their elements. An element is made of one type of atom. Compounds are chemical combinations of different types of atoms. Compounds and the elements that make them up often have different properties. cupcakes—flour, baking soda, salt, sugar, eggs, vanilla, milk, baking soda, salt, sugar, cupcakes—flour, and chemical and butter—all have unique physical the ingredients together and properties. But when you mix The cupcakes bake them, a new product results—cupcakes. that are different from the have properties after being baked From Elements to Compounds Elements From Elements and Chemical Bonds Chemical and Elements Formulas, Chemical Compounds, Bonds and Covalent
How is a How 8
d d n i . 8 0 4 9 8 8 Key Concept Check Concept Key _ 2 L _ LESSON 2 LESSON Bonds Elements and Chemical Reading Essentials E CHAPTER 8 CHAPTER properties of a covalent compound? a polar is water Why compound? How do elements differ do elements differ How they the compounds from form? some common What are R _ 3TUDY #OACH 3 compound different from the from different compound elements that make it up? 140 1. Differentiate details under each heading. details under each heading. review outline to your Use the lesson. Make an Outline an Outline Make in Outline the information the headings this lesson. Use as the main divisions of your Include importantoutline. • Key Concepts Concepts Key • • 1 0 _ 8 0 0 _ 2 3 3 CC332_008_013_RE_L2_889408.indd 8 CC332_008_013_RE_L2_889408.indd 9 3 3 2 _ 0 0 8 _ 0 1 3 _ R E
_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 2 _ 8 8 9 4 0 edn setas lmnsadCeia od ElementsandChemicalBonds Reading Essentials Shared Electrons Arrangement Electron A NobleGas Covalent Sharing Bonds—Electron valence electrons.Itformsonebondtobecomestable. bonds tobecomestable.Ahydrogenatomisstablewithtwo valence electrons.Therefore,anoxygenatomformstwo becomesstablebyformingchemicalbondsuntilithaseight noble gas.Ana valence electrons.Thisisthesameelectronarrangementasa valence electrons. one valenceelectron.Theoxygenatomisunstablewithsix chemically unstable.Eachhydrogenatomisunstablewith shown inthefigurebelow. Beforethereaction,atomsare compound isstable. atoms havetheelectronarrangementofanoblegas.The a result, oxygennowhaseightvalenceelectrons. Allthree The oxygenatombondedwithtwohydrogenatoms.As figure. Eachhydrogenatomnowhastwovalenceelectrons. bond. Theycountas valence electronsforbothatoms. from theoxygenatom.Theseelectronsaresharedin valence electrons—onefromthehydrogenatomandone stable covalentcompound.Eachbondhastwo They sharedtheirunpairedvalenceelectronsandformeda atom and thehydrogenatomsbecomechemically stable? compound. pairs ofvalence electrons bond bond, theydothisbysharingvalenceelectrons. sharing valenceelectrons.Whenunstable,nonmetalatoms 8 . i n d lcrn1electron 1 electron d Recall thatmostatomsarechemicallystablewitheight Hydrogen andoxygencanreacttoformwater(H Recall thatatomscanbecomemorechemicallystableby Look atthedotdiagramforwater, ontherightside ofthe Look againatthefigureabove.Howdidoxygen
9
is achemical atomsshare bondformedwhentwo oneormore H 2 electrons 6 electrons tom with less than eight valence electrons tom withlessthaneightvalenceelectrons . Theatomsthenformastablecovalent O 2H + O H A
covalent 2 O), as oxygen atom have before valence didthe electrons 2. State bonds. double, andtriplecovalent information aboutsingle, note cards to organize threeMake quarter-sheet bonding? Visual Check
Triple Covalent Bonds
H Double Covalent Bonds 2 How many O
Single Covalent Bonds H O H 22/24/10 11:50:48AM 141 / 2 4 / 1 0
1 1 : 5 0 : 4 8
A M M A
1 5 : 0 5 : 1 1
0 1 / 4 2 /
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/24/10 11:50:51 AM
. Table sugar is a covalent . Table In a hydrogen molecule, each molecule, In a hydrogen its valence shares atom hydrogen a forming electron with the other, bond. single covalent In a carbon dioxide molecule, the molecule, In a carbon dioxide 2 pairs of shares carbon atom atom, electrons with each oxygen bond. forming a double covalent In a nitrogen molecule, each molecule, In a nitrogen 3 valence shares atom nitrogen forming a electrons with the other, bond. triple covalent O N H C H N O is a group of atoms held together by covalent covalent by of atoms held together is a group . One molecule contains 12 carbon atoms, 11 O 22 molecule
H O A 12 N + H Triple Covalent Bond Covalent Triple Single Covalent Bond Single Covalent C + + Double Covalent Bond Double Covalent H The chemically stable unit of a covalent compound is a When two or more atoms share valence electrons, they When two or more atoms share Look at the figure below. In a single covalent bond, bond, covalent a single In figure below. at the Look N + properties. They usually have low melting points and low properties. They usually have low boiling points. They are also usually gases or liquids at room temperature, but they can be solids. Covalent compounds are poor conductors of thermal energy and electricity. molecule. form a stable covalent compound. The covalent compound’s The covalent compound’s form a stable covalent compound. but they share similar carbon dioxide and water are different, two atoms share one pair of valence electrons. In a double electrons. In a pair of valence share one atoms two of valence share two pairs bond, two atoms covalent three atoms share bond, two In a triple covalent electrons. that two The more electrons valence electrons. pairs of between stronger the covalent bond is atoms share, the bonds. Triple are stronger than single them. Double bonds than double bonds. bonds are stronger 22 hydrogen atoms, and 11 oxygen atoms. All these atoms The only way to further are covalently bonded together. break down the molecule would be to chemically separate of sugar the carbon, hydrogen, and oxygen atoms. Trillions molecules make up one grain of sugar. Molecules Covalent Covalent Compounds Double and Triple Covalent Bonds Covalent Triple and Double bonding that acts as an independent unit compound. The chemical formula for a molecule of table sugar is C O ) or 2 What are What are )? Why? Is the bond Is the bond 0 2 1
d d n i . 8 0 4 9 8 8 Key Concept Check Concept Key _ 2 L Visual Check Visual _ Bonds Elements and Chemical Reading Essentials E R _ unstable with 1 unpaired unstable with 1 unpaired electron. valence Each hydrogen atom is chemically atom Each hydrogen unstable with 2 unpaired valence valence unstable with 2 unpaired is unstable atom A carbon electrons. electrons. valence with 4 unpaired Each oxygen atom is chemically atom Each oxygen unstable with 3 unpaired unstable with 3 unpaired electrons. valence Each nitrogen atom is chemically atom Each nitrogen 3 nitrogen gas (N nitrogen 142
4. Summarize
stronger between atoms atoms between stronger gas (H in hydrogen 3. Compare some common propertiessome common of compounds? covalent 1 0 _ 8 0 0 _ 2 3 3 CC332_008_013_RE_L2_889408.indd 10 CC332_008_013_RE_L2_889408.indd 11 3 3 2 _ 0 0 8 _ 0 1 3 _ R E
_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 2 _ 8 8 9 4 0 (Partial negative charge) edn setas lmnsadCeia od ElementsandChemicalBonds Reading Essentials nonpolar compounds. compounds. Nonpolarcompoundsdissolveinother “like dissolveslike.”Polarcompoundsdissolveinotherpolar not dissolveinwater, whichisapolarcompound.However, compound. Forexample,oilisanonpolarItwill shared electrons. carbon atomandtheoxygenatomspullequallyon the right above.Thismoleculeisalsononpolar becausethe Nonpolar Molecules Water Polar andOther Molecules carbon dioxidemolecule,CO identical, theirattractionforsharedelectronsisequal.A nonpolar molecule.Becausethetwohydrogenatomsare shared valenceelectrons.Ahydrogenmolecule,H watermolecules. molecules toseparatefromoneanotherandmixwiththe the negativeendofasugarmolecule.Thiscauses molecule. Also,thepositiveendofawatermoleculepullson a watermoleculepullsonthepositiveendofsugar because bothsugarandwaterarepolar. Thenegativeendof properties. Sugar, forexample,dissolveseasilyinwater because ofunequal sharingofelectrons. negative end positive endandapartial molecule thathasapartial As aresult,watermoleculeispolar. charge. Thehydrogenatomshaveapartialpositive negative charge,theoxygenatomhasapartial pulled closertotheoxygenatom.Becauseelectronshavea hydrogen atomdoes.Asaresult,thesharedelectronsare atom attractstheelectronsmorestronglythaneach molecule, showninthemodelbelowonleft,oxygen electrons morestronglythantheotheratomcan.Inawater (Partial positive charge) 8 . i n d d A nonpolarcompoundwillnoteasilydissolveinapolar The chargesontheendsofapolarmoleculeaffectits In acovalentbond,oneatomcanattracttheshared A moleculeisnonpolarifitsatomspullequallyonthe
(
1 + 1 ) Polar ( - ) ( + ) H — O — H 2 , isshowninthemodelon Nonpolar A
polar molecule 2 , isa O is a — — C — — O partial positive charge? partial in awater moleculehave a 7. Infer 6. Identify 5. State mix tablesaltwithwater, and know? or nonpolar?How doyou molecules oftablesaltpolar the saltdissolves. Are the polar compound? Visual Check Key Concept Check Imagine thatyouImagine Why iswater a Which atoms 22/24/10 11:50:57AM 143 / 2 4 / 1 0
1 1 : 5 0 : 5 7
A M M A
4 0 : 1 5 : 1 1
0 1 / 4 2 /
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/24/10 11:51:04 AM O O — — C C — — O O ) contains two atoms ) contains two 2 is made up of carbon (C) is made up of carbon 2 is a group of chemical symbols and symbols and of chemical is a group . Just as a recipe lists the a recipe lists the . Just as Shows atoms and valence and valence atoms Shows and lines; atoms Shows and atoms Balls represent represent Spheres are shown below. are shown below. • • • • 2 Dot Diagram electrons Structural Formula one each line represents pair of electrons shared Ball-and-Stick Model bonds; sticks represent bond angles show used to Space-Filling Model show used to atoms; three-dimensional atoms of arrangement The small number after a chemical symbol The small number example, the chemical formula for carbon example, the chemical chemical formula chemical . The formula uses chemical symbols to identifyformula uses . The
2 A can show the molecule in a different way. Common way. can show the molecule in a different How do you know which elements make up a make which elements know do you How A chemical formula identifies the types of atoms in a A chemical formula identifies compound? compound? is a subscript. A subscript shows the number of atoms of that subscript shows the number is a subscript. A a subscript compound. A symbol without element in the Carbon dioxide (CO means one atom. and oxygen (O). and oxygen (O). Chemical Formulas and Molecular Models Molecular and Formulas Chemical the elements in the compound. CO the elements in of oxygen bonded to one atom of carbon. of oxygen bonded a formula does not compound or a molecule. However, of the molecule. Models explain the shape or appearance about a molecule. Each can provide different information one types of models for CO numbers that represent the elements and the number of atoms of each number elements and the the that represent numbers up a compound make element that in a lists the elements formula chemical a ingredients, compound. For dioxide is CO 2 The 2 indicates two atoms of atoms two 2 indicates The Each molecule of oxygen. two has carbon dioxide atoms. oxygen CO Chemical Formula 2 According According 1
What d d n i . 8 A carbon dioxide molecule is made up A carbon dioxide atoms. (O) and oxygen of carbon (C) 0 4 9 8 8 _ 2 Reading Check L Visual Check Visual _ Bonds Elements and Chemical Reading Essentials E R _ indicates one atom. Each one atom. indicates molecule of carbon dioxide has one carbon atom. A symbol without a subscript 3 144 9. Interpret 9. Interpret 8. Specify in a is given information chemical formula? to the to structural formula, pairs of shared many how in a molecule electrons are of carbon dioxide? 1 0 _ 8 0 0 _ 2 3 3 CC332_008_013_RE_L2_889408.indd 12 CC332_008_013_RE_L2_889408.indd 13 3 3 2 _ 0 0 8 _ 0 1 3 _ R E
_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 2 _ 8 8 9 4 0 edn setas lmnsadCeia od ElementsandChemicalBonds Reading Essentials 3. 2. 1. covalent bond: formula: chemical Mini Glossary
8 . lcrn hrdthree pairsofelectrons hydrogen gas Example shared Electrons i What doyouthink n Did you changeyour mind? agree withthestatement oraDifyou disagree. lesson. Fill intheAfter column withanAifyou Reread thestatements atthebeginning ofthe d Complete thetablebelowtocomparedifferenttypesofcovalentbonds. is C what thechemicalformulaofglucose,asimplesugar, means.Glucose’s chemicalformula Review thetermsandtheirdefinitionsinMiniGlossary. Write asentenceexplaining compounds, covalentbonds,andchemicalformulas? How didmakinganoutlineofthelessonhelpyouorganizeinformationabout d share oneormore pairsofvalence electrons of atoms ofeachelement that make upacompound numbers that represent theelements andthenumber
1 3 6 H 12 O 6 . a chemicalbondformedwhentwo atoms a group ofchemicalsymbolsand igeBn obeBn Triple Bond DoubleBond Single Bond polar molecule: polar molecule: molecule: lesson’s resources. and access your textbook to findthis Log onto ConnectED.mcgraw-hill.com that acts asanindependentthat unit acts electrons negative endbecauseofunequalsharing and apartial C onnect a group ofatoms heldtogether by covalent bonding ED a molecule that has a partial positive enda moleculethat hasapartial LESSON END OF 22/24/10 11:51:06AM 145 / 2 4 / 1 0
1 1 : 5 1 : 0 6
A M Name Date Class
Content Vocabulary LESSON 2 Compounds, Chemical Formulas, and Covalent Bonds Directions: Complete this chart by providing an example for each term below. Then write a brief definition.
Term Example and Definition Bond 1.
Chemical formula 2.
Covalent bond 3. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Molecule 4.
Polar molecule 5.
26 Elements and Chemical Bonds
CC332_025_031_CRF_L2_891475.indd332_025_031_CRF_L2_891475.indd 2626 110/7/090/7/09 88:49:05:49:05 PMPM Name Date Class
Lesson Outline LESSON 2 Compounds, Chemical Formulas, and Covalent Bonds
A. From Elements to Compounds 1. Compounds are chemical combinations of two or more . 2. Compounds and the elements that form them often have very different chemical and physical . 3. Atoms can bond to form compounds by valence electrons. 4. A(n) is a group of chemical symbols and numbers that represent the elements and the numbers of atoms of each element in a compound. 5. The letters in a chemical formula represent . 6. show the shape and appearance of the arrangement of atoms in a compound. B. Covalent Bonds—Electron Sharing 1. A(n) is a chemical bond formed when two or more atoms share one or more pairs of valence electrons. 2. When forming water, valence electrons are between oxygen and hydrogen atoms, thereby forming covalent bonds to make three stable atoms. C. Covalent Compounds 1. A(n) is a group of atoms held together by covalent bonding that acts as an independent unit. 2. generally have low melting points and low boiling points. They are conductors of electricity. a. In a hydrogen molecule, a(n) covalent bond forms when each atom shares its valence electrons with the other. b. In a carbon dioxide molecule, a double covalent bond forms when the carbon atom shares pairs of valence electrons with each oxygen atom.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. The McGraw-Hill of a division © Glencoe/McGraw-Hill, Copyright
Elements and Chemical Bonds 27
CC332_025_031_CRF_L2_891475.indd332_025_031_CRF_L2_891475.indd 2727 110/7/090/7/09 88:49:06:49:06 PMPM Name Date Class
Lesson Outline continued
c. In a(n) covalent bond, three pairs of valence electrons are shared between two atoms. d. covalent bonds are stronger than covalent bonds, which are stronger than single covalent bonds. 3. In a covalent bond, one atom can attract the shared electrons more than the other atom can. a. In a molecule of water, the atom attracts the electrons more strongly than each hydrogen atom does. b. Because the electrons have a slight negative charge, there is a slight negative charge near the atom; there is a slight charge near the hydrogen atoms. c. A molecule that has a slight positive end and a slight negative end because of unequal sharing of electrons is a(n) . d. Polar molecules, such as sugar and water, easily in one another because of the attraction of opposite charges. 4. Molecules made up of atoms of the same element are because the atoms are identical. So, they share electrons equally. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
28 Elements and Chemical Bonds
CC332_025_031_CRF_L2_891475.indd332_025_031_CRF_L2_891475.indd 2828 110/7/090/7/09 88:49:06:49:06 PMPM M P
6 2 : 3 0 : 2 1
0 1 / 4 2 /
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/24/10 12:03:26 PM . Because electrons have a Read the two statements below and decide below statements Read the two is an atom that is no longer electrically neutral because because neutral is an atom that is no longer electrically
chemically stable. good electricalMetals are conductors because electrons valence their hold onto to they tend very tightly. Losing electrons can make some atoms more more electrons can make some atoms Losing 6. 5. ion An As you read in Lesson 2, the atoms of two or more As you read in Lesson 2, the atoms When an atom loses or gains a valence electron, it becomes Before Statement After What do you think? do you What column A in the Before an Place with them. or disagree agree whether you read you’ve After disagree. or a D if you with the statement agree if you mind. changed your have see if you to statements the this lesson, reread positive charge. An atom that gains valence electrons becomes an ion with a negative charge. This is because the number of protons is now less than the number of electrons. atoms with the same number of valence electrons as a atoms with the same number noble gas. an ion. electrons has lost or gained valence it negative charge, gaining or losing an electron changes the overall charge of the atom. An atom that loses valence electrons becomes an ion with a positive charge. This is because after an atom loses an electron, the atom has more protons than electrons. The atom is now an ion with a nonmetals form compounds by sharing valence electrons. nonmetals form compounds by they do not when a metal and a nonmetal bond, However, more valence electrons share electrons. Instead, one or to the nonmetal atom. After transfers from the metal atom the atoms bond and form a chemically electrons transfer, valence electrons results in stable compound. Transferring Understanding Ions Elements and Chemical Bonds Chemical and Elements Metallic Bonds Ionic and
4 1
As you read, read, you As
Why does an Why d d n i . 8 0 4 9 8 8 _ 3 Reading Check L _ LESSON 3 LESSON Bonds Elements and Chemical Reading Essentials E CHAPTER 8 CHAPTER What is an ionic compound? bonds do metallic How and covalent from differ ionic bonds? R _ 3TUDY #OACH 8 146
1. Explain a partner and take each quiz. other’s Write a Quiz Write each for one question write on one side of a paragraph the Write sheet of paper. on the back of the answers with quizzes Exchange paper. Key Concepts Concepts Key • • negative charge? negative atom that gains an electron atom an ion with a become 1 0 _ 4 1 0 _ 2 3 3 CC332_014_018_RE_L3_889408.indd 14 CC332_014_018_RE_L3_889408.indd 15 3 3 2 _ 0 1 4 _ 0 1 8 _ R E
_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 3 _ 8 8 9 4 0 sign. a negatively chargedion.Thisisshownbyanegative( When achlorineatomgainsvalenceelectron,itbecomes a positivelychargedion.Thisisshownbyplus( edn setas lmnsadCeia od ElementsandChemicalBonds Reading Essentials ValenceGaining Electrons Losing ValenceElectrons electron arrangementasthestablenoblegasargon(Ar). will haveeightvalenceelectrons.Itthenthesame figure below. Ifachlorineatomgainsonevalenceelectron,it Chlorine atomshavesevenvalenceelectrons,asshowninthe gas. Thenonmetalchlorine(Cl)hasanatomicnumberof17. Either way, theyachievetheelectronarrangementofanoble atoms canalsogainvalenceelectronsfrommetalatoms. valence electronswithothernonmetalatoms.Nonmetal neon (Ne).Thesodiumatomischemicallystable. then haseightvalenceelectrons,thesameasnoblegas level becomethenewvalenceelectrons.Thesodiumatom one valenceelectron,theelectronsinnext-lowerenergy and gainingvalanceelectrons.Whenasodiumatomloses a nonmetal. Thefigurebelowdescribestheprocessoflosing they losevalenceelectronsandformachemicalbondwith atoms haveonevalenceelectronandarechemicallyunstable. Sodium isingroup1ontheperiodictable.Therefore,sodium means eachsodiumatomhas11protonsandelectrons. 8 Neutral Neutral . 8 electrons. its outer energy level willhave electrons. Ifitgains1electron, A chlorineatom has7valence have 8electrons. outer itsnext levelelectron, will Ifitlosesits1valenceelectron. A sodiumatom has1valence i n d d In Lesson 2, you learned that nonmetal atoms can share In Lesson2,youlearnedthatnonmetalatomscanshare Metal atoms,suchassodium,becomemorestablewhen Sodium (Na)isametal.Itsatomicnumber11.This Whenasodiumatomlosesvalenceelectron,itbecomes
1 5
ntbeAo StableIon Unstable Atom ntbeAo StableIon Unstable Atom neon (Ne)andisstable. arrangementhas theelectron of sodium apositive charge. Itnow Losing 1valence gives electron ment ofargon (Ar) andisstable. It now arrange- hastheelectron chlorine atom anegative charge. givesGaining 1electron the ( ( - + + ) ) ) sign. - ) electrons? likely to gainorlosevalence a group 16elementmore 2 Predict 2. 3. Identify metallic compounds. information aboutionicand note cards to summarize two quarter-sheet Make gained two electrons? ion’s charge beiftheatom Visual Check Reading Check
Compounds Metallic Are atoms of What would an
Com
Ion
pounds
ic 22/24/10 12:03:31PM 147 / 2 4 / 1 0
1 2 : 0 3 : 3 1
P M M P
5 3 : 3 0 : 2 1
0 1 / 4 2 /
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/24/10 12:03:35 PM . - 3 - 8 electrons 8 electrons 2 electrons Cl NaCl sodium atom + harged ion. ionic bond. ionic bond. Na 8 electrons 2 electrons 3 charge ). Once an atom ). Once - salt, a
- = electron is transferred to a electron is transferred a negatively c The attraction between positively and between positively The attraction 3 charge. This is written as N 3 charge. This is Cl - 10 electrons Cl (NaCl), or table 7 electrons 8 electrons 2 electrons ) and electrons ( ) and electrons - + he sodium atom is now a positively charged he sodium atom is now a positively shown below. shown below. + 7 protons + 1 electron 8 electrons 2 electrons Na A nitrogen ion has a A nitrogen ion Recall that in a covalent bond, two or more nonmetal The ions of ionic compounds are strongly attracted to each Atoms are electrically neutral because they have the same same have the they because neutral are electrically Atoms and atoms lose valence electrons Recall that metal Na compounds are made up of many molecules. However, when compounds are made up of many molecules. However, nonmetal ions bond to metal ions in an ionic compound, there are no molecules. Instead, there is a large collection of ions with opposite charges. The ions are all attracted to each other and are held together by ionic bonds. atoms share electrons and form a unit, or molecule. Covalent atoms share electrons and form a unit, or molecule. Covalent These ions attract each other and form a stable ionic and form a stable ionic These ions attract each other compound, as an is ions in an ionic compound charged negatively nonmetal atoms gain valence electrons. When forming a nonmetal atoms gain valence atoms gain the electrons lost chemical bond, the nonmetal metal atoms. In by the The loses one valence electron. chlorine atom. T ion. The chlorine atom is now number of protons ( number ion. For it becomes a charged loses electrons, gains or (N) is 7. This for nitrogen the atomic number example, It is and 7 electrons. has 7 protons each N atom means that N atoms When forming an ionic bond, electrically neutral. To The N ion then has 10 electrons. gain 3 electrons. number of of the ion, subtract the determine the charge ion from the number of protons. electrons in the Ionic Compounds Compounds Ionic and Covalent Comparing Ionic Bonds—Electron Transferring Ionic Bonds—Electron Determining an Ion’s Charge Ion’s an Determining other. As a result, ionic compounds are usually solid and As a result, ionic other. brittle at room temperature. They have relatively high melting that contains dissolved ionic and boiling points. Water This is because compounds is a good conductor of electricity. an electrical charge can pass from ion to ion in the solution.
0.45 84 pm -
) is 45% - -
= 2 -
= = 6 1
What holds d d 100 n 186 pm i . 8 × 186 pm 0 ÷ 4 9 - 8 8 Key Concept Check Concept Key _ ion is 102 pm. By what ion is 102 pm. By 0.45 3 L + _ - Divide the difference by by Divide the difference radius. the atom’s from the atom’s radius. the atom’s from Subtract the ion’s radius Subtract the ion’s Bonds Elements and Chemical Reading Essentials Multiply the answer by by Multiply the answer 100 and add a % sign. E 84 pm
R
_ Math Skills Math - 8 148 5. Explain 4. Calculate Percentage Percentage 4. Calculate (O) an oxygen radius of The radius The pm. is 73 atom ion (O of an oxygen c. b. the radius of a sodium (Na) the radius of a sodium radius of The is 186 pm. atom a Na a. An atom’s radius is measured measured radius is An atom’s (pm), 1 trillion in picometers than a meter. times smaller an becomes atom When an either increases ion, its radius example, For or decreases. does the radius change? does the radius work. your Show 140 pm. By what percentage 140 pm. By what percentage A negative value means a value means A negative A positive in size. decrease value means an increase. ionic compounds together? ionic compounds 102 pm percentage does the radius the radius does percentage forms? change as the ion 1 0 _ 4 1 0 _ 2 3 3 CC332_014_018_RE_L3_889408.indd 16 CC332_014_018_RE_L3_889408.indd 17 3 3 2 _ 0 1 4 _ 0 1 8 _ R E
_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 3 _ 8 8 9 4 0 bonds thatyoustudiedinthischapter. The tablebelowcomparesthecovalent,ionic,andmetallic because thevalenceelectronsatsurfaceinteractwithlight. electron seaandmovetonewpositions.Metalsareshiny not break.Themetalionscanslidepastoneanotherinthe metal ishammeredintoasheetordrawnwire,itdoes to ion, theycaneasilyconductanelectriccharge.Whena electricity. Becausethevalenceelectronscanmovefromion edn setas lmnsadCeia od ElementsandChemicalBonds Reading Essentials ofMetallic CompoundsProperties PoolingMetallic Bonds—Electron the positiveions. not bondtooneatom.Instead,a“seaofelectrons”surrounds electrons movefromionto and becomepositiveions.T electrons bond formedwhenmany metalatomsshare theirpooledvalence electrons, asshowninthetablebelow. with oneanother when formingcompounds.Metal 8 Metallic Ionic electrons Covalent . Type of Bond What is bonding? Properties ofCompounds Properties What isbonding? Type ofBond i n d d Metalsaregoodconductorsofthermalenergyand Recall thatmetalatomstypicallylosevalenceelectrons
Al Al 1 —transfer valence electrons 7 + + . Inaluminum(Al),atoms —pool valence electrons —share valence Na Al + Aluminum + ( + Water ) Salt ( Al Al - + + ) Cl ( + by combining,orpooling,theirvalence - ) Al H
+ — O — Al Al + + ion. Valence electronsinmetalsdo he negativelychargedvalence nonmetal atoms; nonmetal atoms atoms formcompounds lose theirvalence nonmetal ions; metal ions; metal ions metal ions A metallic bond electrons solids are ofthermalenergy poorconductors • dissolves inwater • highmeltingandboilingpoints • • solid crystals • dull appearance ofthermalenergypoor conductors and • notableto often dissolve inwater • low meltingandboilingpoints • gas, liquid, orsolid • can behammered into sheetsandpulledinto • • shiny surface ofthermalenergygood conductors and • donotdissolve inwater • highmeltingandboilingpoints • usuallysolidatroom temperature • ionic compounds inwater solutionsconduct • and electricity electricity wires electricity electricity is a teml nry well. energy thermal compound thatconducts bond thatresults ina 7 Identify 7. A another? atoms bondwithone Specify 6. flow through whichsomethingcan (verb) conduct CADEMIC Visual Check Key Concept Check to serve asamedium toserve V How dometal OCABULARY Circle the 22/24/10 12:03:49PM 149 / 2 4 / 1 0
1 2 : 0 3 : 4 9
P M M P
9 5 : 3 0 : 2 1
0 1 / 4 2 /
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 22/24/10 12:03:59 PM END OF LESSON aluminum . In each covalent metal 5. metal to metal to and 2. a bond formed when many metal atoms share share metal atoms when many a bond formed ED onnect C transfer valence electrons, pool valence transfer valence electrons, table salt their pooled valence electrons valence their pooled ionic, metallic, Log on to ConnectED.mcgraw-hill.com ConnectED.mcgraw-hill.com on to Log find this to textbook your and access resources. lesson’s metallic bond: metallic bond: Bonds ionic . metal in this chapter: 4. nonmetal to nonmetal to water share valence electrons share 8 1
d d or n the attraction between positively and negatively and negatively positively the attraction between i . 8 0 4 9 8 8 _ 3 an atom that is no longer electrically because it has that neutral an atom L lost or gained valence electrons valence lost or gained charged ions in an ionic compound ions in an charged _ Bonds Elements and Chemical Reading Essentials E bottom box, identify the type of bond by writing bottom box, identify the type electrons, Fill in the organizer below with the following terms to compare the three types of Fill in the organizer below with bonding that you learned about Review the terms and their definitions in the Mini Glossary. Write two sentences that two sentences that Write Mini Glossary. and their definitions in the Review the terms ion. ion and a negatively charged between a positively charged describe the difference nonmetal agree with the statement or a D if you disagree. disagree. or a D if you the statement with agree mind? change your Did you Reread the statements at the beginning of the at the beginning the statements Reread with an A if you column in the After lesson. Fill R What do you think nonmetal to nonmetal to 3. _ 1. 8 150 2. 1. Mini Glossary ion: ionic bond: 1 0 _ 4 1 0 _ 2 3 3 CC332_014_018_RE_L3_889408.indd 18 Name Date Class
Content Vocabulary LESSON 3 Ionic and Metallic Bonds Directions: In this word search puzzle, find and circle the four terms listed below. Then write each term on the line before its definition.
conduct ion ionic bond metallic bond
UUKNOMVMHR R TCZEYEXOTOC ZVCHGTPCNC I ERFLNARA IOG UQ J T P L YOMN I ZKZNALNKZTC KRUPF I ZUFVO F JCHCCXUUSN HECBABXFTED FAORGOZVYOU SNP I JNETHKC DYSCQD I SS J T Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 1. to serve as a medium through which something can flow
2. a chemical bond between positively and negatively charged ions
3. a chemical bond between metal atoms
4. an atom that has lost or gained valence electrons
44 Elements and Chemical Bonds
CC332_043_049_CRF_L3_891475.indd332_043_049_CRF_L3_891475.indd 4444 110/7/090/7/09 88:55:26:55:26 PMPM Name Date Class
Lesson Outline LESSON 3 Ionic and Metallic Bonds
A. Understanding Ions 1. When a metal and a(n) bond, they do not share electrons. 2. The atom transfers one or more valence electrons to the atom, forming a chemically stable compound. 3. A(n) is an atom that is no longer electrically neutral because it has lost or gained one or more valence electrons. a. An atom that loses one or more valence electrons becomes an ion with a(n) charge. b. An atom that gains one or more valence electrons becomes and ion with a(n) charge. 4. Sodium is a metal that has valence electron(s). a. To become stable, sodium has to a valence electron. b. When a sodium atom loses a valence electron, it becomes a(n) charged ion. 5. Chlorine is a nonmetal that has valence electron(s). a. To become stable, chlorine has to a valence electron. b. When a chlorine atom gains a valence electron, it becomes a(n) charged ion. 6. To figure out the charge of an ion, the number of electrons in the ion from the number of . B. Ionic Bonds––Electron Transferring 1. When forming a chemical compound, the nonmetal atoms the electrons by the metal atoms. 2. Due to the change in the number of electrons, the metal and nonmetal atoms both
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. The McGraw-Hill of a division © Glencoe/McGraw-Hill, Copyright become . 3. The attraction between positively and negatively charged ions in an ionic compound is a(n) .
Elements and Chemical Bonds 45
CC332_043_049_CRF_L3_891475.indd332_043_049_CRF_L3_891475.indd 4545 110/7/090/7/09 88:55:26:55:26 PMPM Name Date Class
Lesson Outline continued
C. Ionic Compounds 1. Most ionic compounds are and at room temperature. a. Ionic compounds usually have melting points and boiling points. b. Ionic compounds are conductors of electricity because electric charge passes easily from one ion to another. 2. Covalent compounds form when atoms of different nonmetals electrons, forming bonds. a. Covalent compounds are made up of many . b. In contrast, compounds are composed of a large collection of , all of which attract each other and are held together by bonds. D. Metallic Bonds—Electron Pooling 1. Metal atoms form compounds with other by combining, or pooling, their valence electrons.
2. A(n) is a bond formed when many metal atoms share Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. their pooled valence electrons. a. When metal atoms lose their , they become ions. b. Valence electrons in metals are not bonded to any particular atom; instead, metal ions are surrounded by a sea of . 3. Metals are conductors of electricity because their valence electrons can easily move from ion to ion, transferring electric charge. 4. Metals can be hammered into a sheet or drawn into a wire because the ions slide past one another through the electron pool. 5. Metals are shiny because the at their surface interact with light.
46 Elements and Chemical Bonds
CC332_043_049_CRF_L3_891475.indd332_043_049_CRF_L3_891475.indd 4646 110/7/090/7/09 88:55:27:55:27 PMPM