Chemical Bonds - Putnam High School Freshmen Academy Science - Home

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Chapter Resources

Chemical Bonds

Includes:

Reproducible Student Pages

ASSESSMENT

Chapter Tests

Chapter Review

HANDS-ON ACTIVITIES

Lab Worksheets for each Student Edition Lab

Two additional Laboratory Activities

Foldables–Reading and Study Skills activity sheet

MEETING INDIVIDUAL NEEDS

Directed Reading for Content Mastery

Directed Reading for Content Mastery in Spanish

Reinforcement

Enrichment

Note-taking Worksheets

TRANSPARENCY ACTIVITIES

Section Focus Transparency Activities

Teaching Transparency Activity

Assessment Transparency Activity

Teacher Support and Planning

Content Outline for Teaching

Spanish Resources

Teacher Guide and Answers

Glencoe Science

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1 2 3 4 5 6 7 8 9 10 024 08 07 06 05

Reproducible Student Pages Hands-On Activities

MiniLAB: Try at Home Observing a Bond Type . . . . . . . . . . . . . . . . . . 3MiniLAB: Making a Hydrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Lab: Atomic Trading Cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Lab: Model and Invent Modeling Chemical Bonding. . . . . . . . . . . . . . . 7Laboratory Activity 1: The Five Solutions Problem . . . . . . . . . . . . . . . . 9Laboratory Activity 2: Investigating Covalent and Ionic Bonds. . . . . . 13Foldables: Reading and Study Skills . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Meeting Individual NeedsExtension and Intervention

Directed Reading for Content Mastery . . . . . . . . . . . . . . . . . . . . . . . . 19Directed Reading for Content Mastery in Spanish . . . . . . . . . . . . . . . 23Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Enrichment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Note-taking Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

AssessmentChapter Review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Chapter Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Transparency ActivitiesSection Focus Transparency Activities . . . . . . . . . . . . . . . . . . . . . . . . . 44Teaching Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Assessment Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Chemical Bonds 1

ReproducibleStudent Pages

2 Chemical Bonds

Hands-OnActivities

Hands-On Activities

Chemical Bonds 3

Name Date Class

Observing a Bond Type

Data and Observations

Analysis1. Explain your observations.

2. Relate the attraction between the balloon and the water to the attraction between the northand south poles of two magnets. Why might water act like a magnet?

Procedure 1. Turn on the faucet to produce a thin stream of water.

2. Rub an inflated balloon with wool or fur.

3. Bring the balloon near the stream of water, and describe what you see. Hand

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4 Chemical Bonds

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Making a Hydrate

Procedure 1. Mix 150 g of plaster of paris with 75 mL of water in a small bowl.

2. Let the plaster dry overnight and then take the hardened plaster out of the bowl.

3. Lightly tap the plaster with a rubber hammer.

4. Heat the plaster with a hair dryer on the hottest setting and observe.

5. Place a towel over the sample, then lightly tap the plaster with the hammer after heating it.

Analysis1. What happened to the plaster when you tapped it before and after heating it?

2. What did you observe happening to the plaster as you heated it? Explain.

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Chemical Bonds 5

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Lab PreviewDirections: Answer these questions before you begin the Lab.

1. What information about each element do you need to collect for this lab?

2. What is the relationship between the number of energy levels an atom has and that atom’sposition on the periodic table?

Perhaps you have seen or collected trading cards of famous athletes. Usually,each card has a picture of the athlete on one side with important statisticsrelated to the sport on the back. Atoms also can be identified by their propertiesand statistics.

Real-World ProblemHow can a visible model show how energy levels fill when atoms combine?

Materials4-in 6-in index cardsperiodic table

Goals Display the electrons of elements according to their energy levels. Compare and classify elements according to their outer energy levels.

Procedure1. You will get an assigned element from your

teacher. Write the following informationfor your element on your index card:name, symbol, group number, atomicnumber, atomic mass, and metal,nonmetal, or metalloid.

2. On the other side of your index card, showthe number of protons and neutrons in thenucleus (e.g., 6p for six protons and 6n forsix neutrons for carbon).

3. Draw circles around the nucleus to representthe energy levels of your element. The num-ber of circles you will need is the same as theperiod the element is in on the periodic table.

4. Draw dots on each circle to represent theelectrons in each energy level. Remember,elements in row 1 become stable with twoouter electrons, while levels two and threebecome stable with eight electrons.

5. Look at the picture side only of four or fiveof your classmates’ cards. Identify the elements and the groups to which theybelong.

Atomic Trading Cards

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6 Chemical Bonds

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Conclude and Apply1. As you classify the elements according to their group number, what pattern do you see in the

number of electrons in the outer energy levels?

2. Atoms that give up electrons combine with atoms that gain electrons to form compounds.Predict some pairs of elements that combine in this way.

Communicating Your Data

Make a graph that relates the groups to the number of electrons in their outer energy levels. For more help, refer to the Science Skill Handbook.

(continued)

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Chemical Bonds 7

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Lab PreviewDirections: Answer these questions before you begin the Lab.

1. Why should you wear goggles during this experiment?

2. What is the difference between an ionic bond and a covalent bond?

Chemical bonding is one of the most important concepts in chemistry.Bonding is what makes different compounds. Even though atoms have nuclei containing protons and neutrons, the part of the atom that is mostimportant to chemists is outside the nucleus.

Real-World ProblemHow are electrons involved in chemicalbonding?

Goals Infer chemical formulas by making models

of outer electron levels. Compare and contrast models of ionic and

covalent bonding. Draw and label diagrams to illusrate chemi-

cal bonding.

Possible Materialsmodified egg cartonbeans*pennies*buttons*Alternate materials

Safety Precautions Complete a safety worksheet before you begin.

Make a Model1. Obtain a modified egg carton and beans

from your teacher. The egg carton repre-sents the first and second energy levels ofan atom. The beans represent electrons.

2. Decide which elements you can model bythe number of beans you have. Considerhow the periodic table can be used todetermine the number of outer electrons inan element.

3. Model all the elements that you can createusing the modified egg carton and beans.

4. Draw the models of elements that you cre-ated on a separate piece of paper.

5. Determine if the elements form ionic orcovalent bonding. Record your conclusionson a separate piece of paper.

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.Model and InventModeling Chemical Bonding

8 Chemical Bonds

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Test Your Model1. Look for element combinations that could

represent chemical formulas for com-pounds and molecules. Some formulasmay require more than one atom to formsome types of elements and compounds.

2. Work with other students to make modelsof compounds and molecules produced bychemical bonding.

3. Draw the models of the compounds andmolecules you made on your separate pieceof paper. Record the type of bonding usedto make the compounds and molecules.

Communicating Your Data

Compare your conclusions with other students’ conclusions. What elements did their modelsrepresent? Explain how their elements differed in ability to form ionic and covalent bonds.

Analyze Your Data1. Explain how you can use the periodic table to identify the element that represents your model.

2. Explain whether elements in the metal groups on the periodic table have more or fewer elec-trons in their outer energy levels than the nonmetals.

3. The combinations of elements could represent chemical formulas. Explain why some formulasrequire more than one atom of an element.

Conclude and Apply1. Describe why your model could be used to show examples of both ionic and covalent bonding.

2. Predict what element your model would be if you receive ten beans. Explain your reasoning.

(continued)(continued)

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Chemical Bonds 9

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The Five Solutions Problem

Do you recall the seven dwarfs in the story of Snow White? Their names reflected theirbehaviors. One could recognize them by their actions. Substances can also be identified bytheir behaviors. One way of identifying a substance is by observing how it reacts with otherknown substances. In any chemical reaction, new substances are produced. State, color, andother physical properties of substances produced in a chemical reaction can help identify thesubstances that reacted.

In this experiment, you will classify solutions by how the substances in the solutions react. Usingthis classification, you will identify an unlabeled sample of one of these solutions.

StrategyYou will observe the reactions of five different known solutions, two at a time.You will classify your observations.You will identify an unlabeled sample of one of these solutions.

Materials 96-well microplate sodium carbonate solution, Na2CO3(aq)white paper sodium iodide solution, NaI(aq)plastic microtip pipettes (7) plastic cupdilute hydrochloric acid, HCl(aq) distilled wateriron(III) nitrate solution, Fe(NO3)3(aq) sample of unknown solution 1, 2, 3, 4, or 5silver nitrate solution, AgNO3(aq)

WARNING: Many of these solutions are poisonous. Avoid inhaling any vapors from the solutions. Silvernitrate solution and sodium iodide solution can cause stains. Avoid any contact between them and yourskin or clothing.

LaboratoryActivity11

ProcedurePart A—Observing Reactions of Known

Solutions1. Wear aprons, gloves, and goggles during

this experiment.2. Place the microplate on a piece of white

paper on a flat surface. Have the numberedcolumns of the microplate at the top andthe lettered rows at the left.

3. Using a microtip pipette, place four dropsof the hydrochloric acid solution in each ofwells A1 through F1.

4 Using a clean pipette, place four drops ofthe iron(III) nitrate solution in each ofwells A2 through F2.

5. Repeat step 4 for each of the remainingfour solutions. Use a clean pipette for each.

Place the silver nitrate solution in wells A3through F3, the sodium carbonate solutionin wells A4 through F4, and the sodiumiodide solution in wells A5 through F5.

6. Fill the plastic cup with distilled water, andthoroughly rinse each pipette. Discard thewater.

7. Add four drops of the hydrochloric acidsolution to each of wells A1 through A5.

8. Using another clean pipette, add four dropsof iron(III) nitrate to each of wells B1through B5.

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Data and ObservationsPart A—Observing Reactions of Known Solutions

Table 1

10 Chemical Bonds

Laboratory Activity 1 (continued)

Name Date Class

9. Repeat step 8 for the remaining solutions.Use a clean pipette for each solution. Addthe silver nitrate solution to wells C1through C5, the sodium carbonate solutionto wells D1 through D5, and the sodiumiodide solution to wells E1 through E5. Fig-ure 1 shows the solutions in each of thewells A1 through E5.

10. Observe the contents of each well. Noteany changes in the physical properties ofthe substances in each well. Record yourobservations in Table 1.

Part B—Identifying an Unknown Solution1. Obtain a small sample of an unknown

solution from your teacher. Record thenumber of the solution sample in the firstcolumn of Table 2.

2. Use a clean microtip pipette to add fourdrops of the sample solution to each ofthe wells F1 through F5.

3. Observe the contents of each well. Noteany changes in the physical properties ofthe contents in each well. Record yourobservations in Table 2.

4. Compare the changes that occurred inwells containing the unknown solutionwith the changes that occurred in wellscontaining the known solutions.

A

1 2 3 4 5 6

HClFe(NO

3 )3

AgNO3

Na2 CO

3

NaI

HCl

Fe(NO3)3

AgNO3

Na2CO3

NaI

B

C

D

E

F

SOLUTI

ONS

SOLUTIONS

Figure 1

Solution in Solution AddedMicroplate

HCl Fe(NO3)3 AgNO3 Na2CO3 NaI

1. HCl

2. Fe(NO3)3

3. AgNO3

4. Na2CO3

5. NaI

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Chemical Bonds 11

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Part B—Identifying an Unknown Solution

Table 2

Questions and Conclusions1. What is the identity of the sample solution?

2. What properties of the substances that were formed helped you to identify your sample solution?

3. How did the reactions between the solutions in wells A1 through E5 help you to identify thesample solution?

Unknown Solution solution

HCl Fe(NO3)3 AgNO3 Na2CO3 NaI

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12 Chemical Bonds


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4. Could you use the results of your observations in Part A to identify a solution that is not one ofthe five solutions? Explain.

Strategy Check

Can you classify your observations?

Can you identify an unlabeled sample by the way it reacts with known substances?

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Chemical Bonds 13

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Investigating Covalent andIonic Bonds

All substances are made of atoms. Some of the physical and chemical properties of a substance aredetermined by the chemical bonds that hold its atoms together. In this experiment you will investigatethe properties of compounds formed by two types of chemical bonds—covalent bonds and ionicbonds.

The atoms of covalent compounds are held together by covalent bonds. A covalent bond formswhen two atoms share electrons. In other substances, atoms transfer electrons and form ions. Anion is an atom that has gained or lost electrons. In ionic compounds, the ions are held together byionic bonds.

Solutions of ionic compounds can conduct an electric current. The solutions of covalent com-pounds used in this Lab conduct an electric current. A measure of how well a solution can carryan electric current is called conductivity.

StrategyYou will determine the conductivity of several solutions.You will classify the compounds that were dissolved in the solutions as ionic compounds or

covalent compounds.

Materials 9-V battery and battery clip plastic pipettes (7)10-cm 10-cm cardboard sheet sulfuric acid solution, H2SO4(aq)masking tape sodium chloride solution, NaCl(aq)alligator clips (4) sodium hydroxide solution, NaOH(aq)1000-Ω resistor silver nitrate solution, AgNO3(aq)LED (light-emitting diode) glucose solution, C6H12O6(aq)20-cm lengths of insulated copper wire (2) glycerol solution, C3H8O3(aq)24-well microplate distilled water

WARNING: Sulfuric acid and sodium hydroxide can cause burns. Silver nitrate can cause stains.Avoid inhaling any vapors from the solutions. Avoid any contact between the solutions and your skinor clothing.

LaboratoryActivity22

Procedure

Part A—Constructing a Conductivity Tester1. Attach the 9-V battery clip to the 9-V battery.

Use tape to attach the battery securely to thecardboard sheet, as shown in Figure 1.

2. Attach an alligator clip to one of the leadwires of the 1000-Ω resistor. Connect thesame alligator clip to the red lead wire ofthe battery clip. Tape the resistor and alli-gator clip to the cardboard sheet as shownin Figure 2.

Figure 1

Red lead wire

Black lead wire

Battery clip

9-V battery

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14 Chemical Bonds


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3. Attach an alligator clip to the long lead wireof the light-emitting diode (LED). Connectthis alligator clip to the second wire of the1000-Ω resistor. Tape the alligator clip tothe cardboard sheet.

4. Attach an alligator clip to the short leadwire of the LED. Connect this alligator clipto one end of the insulated copper wires.Tape the alligator clip to the cardboardsheet as shown in Figure 3.

5. Attach the last alligator clip to one end ofthe second insulated copper wire. Connectthe alligator clip to the black lead wire ofthe battery clip. Tape the alligator clip tothe cardboard sheet as shown in Figure 4.

6. Check to be certain that the alligator clips,resistor, and battery are securely taped tothe cardboard sheet and that the clips arenot touching one another.

7. Have your teacher check your conductivitytester.

8. Touch the two ends of the two insulated copper wires, and observe that the LED glows.

1000-Ω resistor

Red lead wire

Alligator clip

Alligator clipInsulated copper wire

Alligator clip

Long lead wire

Short lead wire

LED

Insulated copper wire

Alligator clip

Short lead wire

LED

Black lead wireFigure 2

Figure 3

Figure 4

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Chemical Bonds 15

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Part B—Testing the Conductivity of a Solution1. Wear an apron, gloves, and goggles for Part

B of the experiment.2. Place the microplate on a flat surface. Have

the numbered columns of the microplate atthe top and the lettered rows at the left.

3. Using a clean pipette, add a pipetteful ofthe sulfuric acid solution to well A1.

4. Using another clean pipette, add a pipettefulof the sodium chloride solution to well A2.

5. Repeat step 4 for each remaining solution.Use a clean pipette for each solution. Add thesodium hydroxide solution to well A3, thesilver nitrate solution to well A4, the glucosesolution to well A5, and the glycerol solutionto well A6.

6. Using a clean pipette, add a pipetteful ofdistilled water to well A7. Figure 5 showsthe contents of each of the wells A1through A7.

7. Place the exposed ends of the two insulatedcopper wires into the solution in well A1,positioning the wires so they are at oppositesides of the well. Be sure that the exposedends of the wires are completely submerged.

8. Observe the LED. Use the brightness of theLED as an indication of the conductivity ofthe solution. Rate the conductivity of thesolution using the following symbols:+ (good conductivity); − (fair conductiv-ity); or 0 (no conductivity). Record yourrating in the corresponding well of themicroplate shown in Figure 6.

9. Remove the wires and dry the ends of thewires with a paper towel.

10. Repeat steps 6 through 9 for each remaining solution and the distilled water.

Data and Observations

Figure 6


A

1 2 3 4 5 6

H2 SO

4 (aq)

NaCl(aq)

NaOH(aq)

AgNO3 (aq)

C6 H

12 O6 (aq)

C3 H

8 O3 (aq)

7

H2 O

A

1 2 3 4 5 6 7

Figure 5

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16 Chemical Bonds


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Questions and Conclusions1. What is the conductivity of distilled water?

2. Why was the conductivity of the distilled water measured?

3. What characteristic is common to the compounds that produce solutions that can conductelectricity?

4. What characteristic is shared by the compounds that produce solutions that do not conduct anelectric current?

5. How do the conductivities of solutions of ionic compounds and covalent compounds compare?

Strategy Check

Can you determine the conductivity of solutions?

Can you classify compounds in solutions as ionic or covalent?

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Chemical Bonds 17

Chemical Bonds

Directions: Use this page to label your Foldable at the beginning of the chapter.

H2O

NaCl

C12H22O11

Mg(OH)2

HCl

NH3

SiO2

CaO

HC2H3O2

N2O

C2H5OH

H2SO4

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18 Chemical Bonds

Meeting IndividualNeeds

Meeting Individual Needs

Name Date Class

Chemical Bonds 19

Directions: All of the statements below are false as written. In the space provided, write a term or phrase thatmakes the statement true when it is substituted for the underlined words.

1. The properties of a compound are the same as the propertiesof the elements that it contains.

2. Superscript numbers in chemical formulas tell how manyatoms of each element are found in a unit of compound.

3. All the noble gases except helium have 18 electrons intheir outer energy level.

4. A(n) chemical formula is the force that holds atomstogether in a compound.

5. An ion is a(n) neutral particle that has either more orfewer electrons than protons.

6. Oxidation numbers are written as subscripts.

7. A(n) covalent bond is the force of attraction between theopposite charges of the ions in an ionic compound.

8. The charge on a compound is always positive.

9. Equal sharing of electrons in covalent bonds results inpolar molecules.

10. Only two identical atoms can share electrons unequally.

11. A binary compound contains five different elements.

12. An oxidation number tells how many protons an atommust gain, lose, or share to become stable.

13. The oxidation number of the copper(II) ion is 3+.

14. When writing chemical formulas, add superscripts so thatthe sum of the oxidation numbers equals ten.

15. A polyatomic ion never has a positive or negative charge.

16. The polyatomic ion SO42 is called the sulfide ion.

Directed Reading for

Content Mastery

OverviewChemical Bonds

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20 Chemical Bonds

Section 1 Stability in BondingSection 2 Types of Bonds

Directions: In the blanks, write the terms from the word list that complete the definition. Words can be usedmore than once.

positive element(s) compound(s)

energy level(s) charged number(s)

force(s) atom(s) ion(s) electron(s) negative

1. A chemical formula tells what ____________________ make up a

____________________ and the exact ____________________ of atoms of

each element in a unit of compound.

2. An atom is chemically stable when its outer ____________________ is

completely filled with ____________________.

3. A chemical bond is a ____________________ that holds ____________________

together in a compound.

4. An ____________________ that has lost or gained ____________________ iscalled an ion.

5. An ionic bond is the ____________________ of attraction between the opposite

charges of the ____________________ in an ionic ____________________.

6. The attraction that forms between ____________________ when they share

____________________ is known as a covalent bond.

7. A polar molecule has a slightly ____________________ end and a slightly

____________________ end.

8. A nonpolar molecule does not have oppositely ____________________ ends.

Only atoms that are exactly alike can share their ____________________ equally.


Content Mastery


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Chemical Bonds 21

Directions: The words in each group below are related. Using all the words in the group, write a sentence thatshows how the words are related.

Example: compound, properties, elements

The properties of a compound differ from the properties of the elements that make up the compound.

1. hydrate, compound, water

2. oxidation number, element, electrons

3. zero, oxidation numbers, noble gases

4. oxidation number, Roman numeral, element

5. chemical formulas, neutral, compounds

6. polyatomic, covalent, charged

7. Greek prefixes, binary covalent compounds

8. charge, oxidation number, ionic compounds


Content Mastery

Section 3 Writing Formulas and Naming Compounds

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22 Chemical Bonds

Key Terms Chemical Bonds

Directions: Match each term in Column I with its description in Column II. Write the letter of the correct term inthe space provided.

Column I

1. binary compound

2. chemically stable

3. nonpolar molecule

4. ion

5. ionic bond

6. polar molecule

7. oxidation number

8. chemical formula

9. covalent bond

10. hydrate

11. chemical bond

12. polyatomic ion


Content Mastery

Column II

a. number that indicates how many electronsan atom must gain, lose, or share tobecome stable

b. shorthand that tells what elements a compound contains and the exact number of atoms of each element in a unit of thecompound

c. positively or negatively charged, covalentlybonded group of atoms

d. compound composed of two elements

e. describes an atom that has a full outermostenergy level

f. molecule that has a slightly positive endand a slightly negative end

g. the attraction that forms between atomswhen they share electrons

h. the force that holds atoms together in acompound

i. a compound that has water chemicallyattached to it

j. the force of attraction between the oppositecharges of the ions in an ionic compound

k. molecule made of two identical atoms thatshare the electrons equally

l. a charged particle that has either more orfewer electrons than protons


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Enlaces químicos 23

Instrucciones: Todos los siguientes enunciados son falsos. En el espacio a la derecha, escribe un término o fraseque haga verdadero el enunciado cuando sustituyas la palabra subrayada.

1. Las propiedades de un compuesto son idénticas a laspropiedades de los elementos que contiene el compuesto .

2. Los superíndices en fórmulas químicas indican cuántosátomos de cada elemento hay en una unidad de com-puesto.

3. Todos los gases nobles tienen 18 electrones en su nivelexterno de energía.

4. Un(a) fórmula química es la fuerza que mantiene unidoslos átomos de un compuesto.

5. Un ion es una partícula neutra que tiene más o que tienemenos electrones que protones.

6. Los números de oxidación se escriben como subíndices.

7. Un(a) enlace covalente es la fuerza de atracción entre lascargas opuestas de los iones de un compuesto iónico.

8. La carga de un compuesto siempre es positiva.

9. El compartimiento igual de electrones en los enlacescovalentes resulta en moléculas polares.

10. Sólo dos átomos idénticos pueden compartir electronesdesigualmente.

11. Un compuesto binario contiene cinco elementos diferen-tes.

12. El número de oxidación indica cuántos protones un áto-mo debe ganar, perder o compartir para volverse estable.

13. El número de oxidación del átomo de cobre(II) es 3+.

14. Al escribir fórmulas químicas, añade subíndices de modoque la suma de los números de oxidación sea igual a diez.

15. Un ion polátomico nunca tiene carga positiva o negativa.

16. El ion polátomico SO42- se conoce como ion sulfuro.

Lectura dirigida para

Dominio del contenido

SinopsisEnlaces químicos

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Sección 1 Estabilidad de los enlacesSección 2 Tipos de enlaces

Instrucciones: Escribe en los espacios los términos de la lista que completan cada definición. Puedes usar laspalabras más de una vez.

positivo(a) elemento(s) compuesto(s)

nivel(es) energéticos con carga número(s)

fuerza(s) átomo(s) ion(es) electrón(es) negativa

1. Una fórmula química te indica qué ____________________ forman un

____________________ y el ____________________ exacto de átomos de cada

elemento en una unidad del compuesto.

2. Un átomo es estable químicamente cuando su ____________________ externo

está completamente lleno con ____________________.

3. Un enlace químico es un(a) ____________________ que mantiene

____________________ unidos en un compuesto.

4. Un(a) ____________________ que ha ganado o perdido

____________________ se llama un ion.

5. Un enlace iónico es el(la) _________de atracción entre cargas opuestas del(a)

____________________ en un(a) ____________________ iónico(a).

6. La atracción que se forma entre ____________________ cuando comparten

____________________ se conoce como enlace covalente.

7. Una molécula polar tiene un extremo ligeramente ____________________ y

otro extremo ligeramente ____________________.

8. Una molécula no polar no tiene extremos ____________________ opuesta.

Solamente los átomos que son idénticos pueden compartir sus

____________________ equitativamente.



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Enlaces químicos 25

Instrucciones: Las palabras de cada grupo están relacionadas. Usa todas las palabras en el grupo para escribiruna oración que muestre la relación entre los término.

Ejemplo: compuesto, propiedades, elementos

(Las propiedades de un compuesto son distintas a las propiedades de los elementos que formanel compuesto.)

1. hidrato, compuesto, agua

2. número de oxidación, elemento, electrones

3. cero, números de oxidación, gases nobles

4. número de oxidación, número romano, elemento

5. fórmulas químicas, neutro, compuestos

6. poliatómico, covalente, con carga

7. prefijos griegos, compuestos covalentes binarios

8. carga, número de oxidación, compuestos iónicos



Sección 3 Escribe fórmulas y nombra compuestos

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Términos claves Enlaces químicos

Instrucciones: Relaciona cada término de la Columna I con su descripción en la Columna II. Escribe la letra deltérmino correcto en los espacios de la izquierda.

Columna I

1. compuesto binario

2. químicamente estable

3. molécula no polar

4. ion

5. enlace iónico

6. molécula polar

7. número de oxidación

8. fórmula química

9. enlace covalente

10. hidrato

11. enlace químico

12. ión poliatómico



Columna II

a. número que indica cuántos electronesdebe ganar, perder o compartir unátomo para estabilizarse

b. forma de escritura breve que indica quéelementos contiene un compuesto y elnúmero exacto de átomos de cada ele-mento en una unidad del compuesto

c. grupos de átomos con carga positiva onegativa unidos por enlaces covalentes

d. compuesto formado por dos elementos

e. describe un átomo que tienen su nivelenergético externo lleno

f. molécula que tiene un extremo ligera-mente positivo y otro ligeramentenegativo

g. la atracción que se forma entre átomoscuando comparten electrones

h. fuerza que mantiene a los átomos unidos en un compuesto

i. compuesto que tienen agua unidaquímicamente

j. fuerza de atracción entre las cargasopuestas de los iones en un compuestoiónico

k. molécula formada por dos átomos idén-ticos que comparten electrones equitati-vamente

l. partícula con carga que tiene más omenos electrones que protones

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Chemical Bonds 27

Directions: Each statement below contains a pair of terms or phrases in parentheses. Circle the term or phrasethat makes each statement true.

1. The properties of a compound are (the same as, different from) the properties of the elementsthat make up the compound.

2. Na and Cl are chemical (symbols, formulas).

3. NaCl and NaOH are chemical (symbols, formulas).

4. In the formula H2O, the number 2 is a (subscript, superscript).

5. The number 2 in the formula H2O tells you that each unit of this compound contains two

(hydrogen, oxygen) atoms.

6. If a symbol in a chemical formula does not have a subscript after it, a unit of that compound

contains (no atoms, one atom) of that element.

7. The total number of atoms in Fe2O3 is (two, five, six).

8. There are (three, seven, ten) different elements in H2SO4.

9. An atom is chemically stable if its outer energy level (is filled with, contains no) electrons.

10. For atoms of most noble gases and most other elements, the outer energy level is full when it

has (3, 8) electrons.

11. The noble gases do not readily form compounds because they (are, are not) chemically stable.

12. A chemical bond is a (force, chemical) that holds atoms together in a compound.

13. Chemical bonds form when atoms lose, gain, or (share, multiply) electrons.

Directions: Complete the table below by using the formula of each compound to identify the elements that each compound contains and the number of atoms of each of these elements in a unit of the compound. The firstformula has been done for you.

Stability in BondingReinforcement11

Formula Element 1 Element 2 Element 3

H2O 2 hydrogen 1 oxygen

NaOH

NaCl

NH3

H2SO4

SiO2

14.

15.

16.

17.

18.

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28 Chemical Bonds

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Types of Bonds

Directions: Study the diagram below. Write your answers to the questions in the spaces provided.

Reinforcement22

12P12N

8P8N

A. B.

1. If atom A loses electrons to atom B,a. how many electrons will atom A lose?

b. how many electrons will atom B gain?

c. what will be the oxidation number of atom A?

d. what will be the oxidation number of atom B?

e. what will be the total charge of the compound formed?

f. what type of bond will form?

2. Explain why an element’s oxidation number is related to the group on the periodic table towhich it belongs.

Directions: Complete the table comparing ionic compounds and covalent compounds.

Characteristic Ionic Compounds Covalent Compounds

3. How the compound is formed

4. Smallest particle

5. Usual state at room temperature


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Chemical Bonds 29

Directions: Answer the following questions in the spaces provided. Refer to the periodic table for help.

1. Define an oxidation number.

2. What is the usual oxidation number of oxygen? Of hydrogen?

3. What is the sum of all the oxidation numbers in any compound?

4. Explain the difference between CoCl2 • 6H2O and anhydrous cobalt chloride.

Directions: Use the periodic table in your textbook to identify the oxidation numbers of the elements in each group.

Writing Formulas and NamingCompounds

Reinforcement33

Directions: Write the formulas for the following compounds. Use the periodic table in your textbook for help.10. copper(II) sulfate

11. calcium chloride

12. iron(II) oxide

13. copper(I) oxide

14. sodium sulfide

15. magnesium sulfate heptahydrate

Directions: Complete the following table by providing the name of the compound and the total number ofatoms in each formula given.

Group 1 2 16 17 18

Oxidation number 5. 6. 7. 8. 9.

Formula Name Number of Atoms

16. NH4OH

17. NH4C1

18. Ag2O

19. K2SO4

20. Ca(NO3)2

21. Na2S

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30 Chemical Bonds

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Electron Dot Diagrams

The electrons in an atom’s outer energy level are the electrons that are important to consider inchemical bonds and chemical reactions. These electrons can be represented in a diagram called anelectron dot diagram. The outermost electrons are drawn as dots around the chemical symbol.

In this activity, you will draw electron dot diagrams for several elements.

Enrichment11

Procedure1. Write the symbol for the element. For electron

dot diagrams, this symbol represents thenucleus and all of the electrons of the atomexcept the outermost electrons.

Example: The symbol for chlorine is Cl. In an electrondot diagram, this symbol represents the nucleus andthe ten electrons in the first two energy levels.

2. Use the periodic table to determine howmany outer electrons the element has.Do this by finding to which group the element belongs.

Example: Chlorine belongs to Group 17, the halogens, which have seven outer electrons.

3. Draw a dot to represent each electron in the outer level of the element. Two electrons can be placed on each side of thesymbol. The first two electrons should bepaired on the right side of the symbol.The rest of the outer electrons should bedistributed counterclockwise one by onearound the other sides of the symbol.

Example: The electron dot diagram for chlorine is

Conclude and Apply1. Write electron dot diagrams for the elements listed.

a. hydrogen e. aluminum

b. neon f. fluorine

c. sodium g. argon

d. calcium h. potassium

2. Why do sodium and potassium have the same number of dots in their electron dot diagrams?What does this tell you about the chemistry of these two elements?

Cl


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Chemical Bonds 31

Paper Chromatography

Paper chromatography uses polarity to separate substances from a solution. The polarity of a sub-stance affects how fast a particular substance dissolved in a particular solvent can move along paper.Because the rates of movement are very specific, chromatography can also be used to identify substances.

In paper chromatography, a small sample of a solution is placed on absorbent paper. A solventpasses through the sample and carries the dissolved substances. The various substances in thesolution move outward at different rates.

The procedure described below demonstrates how components of a mixture can be separated.If a procedure is set up in a way that can identify how far the solvent travels and how far the dis-solved substance travels, these distances can be measured and compared. The number obtained bydividing the distance the dissolved substance traveled by the distance the solvent traveled is knownas Rf. If specifics of the procedure such as temperature, solvent, and type of paper are controlled,the Rf values can be used to identify the substances in a solution.

Paper chromatography and other types of chromatography have many uses. An environmentalchemist might use chromatography to identify pollutants in water or a medical chemist to identifypoison or medicines in the blood of a patient.

Enrichment22

Materials petri dish yellow food coloringink round filter papermetric ruler pipe cleanertoothpicksolvent (water, rubbing alcohol, or ethanol)WARNING: Alcohol and ethanol are flammable.

Procedure1. Add a small amount of solvent to a petri dish.2. Use a toothpick to place a small drop of food

coloring at the center of the filter paper.3. Punch a small hole in the center of the filter

paper with the toothpick. Place the pipecleaner through this hole.

4. Carefully place the filter paper on top ofthe petri dish so that the end of the pipecleaner touches the solvent. Observe what

happens as the solvent moves up the pipecleaner and across the filter paper

5. When the solvent has finished moving,remove the filter paper from the dish.Allow the filter paper to dry.

6. Repeat steps 2 through 5 using ink insteadof food coloring. Use a new pipe cleanerand filter paper.

Conclude and Apply1. Why do different bands of color appear on different areas of the filter paper?

2. A student used felt-tip markers to make labels for one of his collections. When water splashedon the labels, the colors began to run and smear. Use your observations from this activity toexplain what happened to the writing.

3. When paper chromatography is used as an analytical tool, the solute and solvent must moveonly in one direction. Explain why this controlled direction is necessary to calculate the Rf.

Pipe cleaner

Filter paper

Petri dishSolvent

Food coloring

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32 Chemical Bonds

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The Crisscross Method

The process of writing chemical formulas canbe made easier by using oxidation numbers.

Remember that the total charge on a compound must be zero. Remember also thatoxidation numbers describe the number ofelectrons an atom or ion gains or loses whenforming compounds. Atoms in the samegroup on the periodic table usually will havethe same oxidation number. Use the periodictable to determine the oxidation numbers ofatoms. Refer to your textbook for oxidationnumbers of polyatomic ions.

Example: Write the formula for barium chloride.

Step 1: Determine the oxidation numbers forthe two elements or ions. Because barium is inGroup 2, its oxidation number is 2+. Elementsin Group 2 tend to lose the two electrons inthe outer energy level, leaving the ions withpositive charges. Chloride is in Group 17, soits oxidation number is 1–. Elements in Group17 have seven electrons in the outer energylevel and tend to gain one electron. The ionsare negative.Step 2: Write the chemical symbols in the correct order, with the metal ion first.

Now, write the oxidation numbers as superscripts. For an ion with an oxidationnumber of 1+ or 1–, write only the sign andnot the number.

Next, crisscross the numbers only—not thesigns this time—writing the oxidation numberof one element as the subscript for the other.Don’t write the number 1 here either.

Step 3: Determine whether the formula is in its simplest form. Reduce the subscripts totheir simplest form by dividing by a commondenominator. The formula for barium chlorideis BaCl2, which cannot be further reduced.Step 4: Check the formula by calculating thetotal positive and total negative charges andconfirming that the total charge on the compound is zero.

OxidationNumber Subscript

Barium (+2) (1) = +2

Chlorine (–1) (2) = –2

Directions: Use the crisscross method to write the chemical formulas for the compounds described below. Checkthat the total charge on each compound equals zero.

1. Write the correct chemical formula for a compound containing barium and oxygen. What isthe name of this compound?

2. Write the formula for zinc iodide, a compound that is used as an antiseptic.

3. One of the uses of ammonium sulfate is in flameproofing fabrics and paper. Write the formulafor ammonium sulfate.

Enrichment33

Ba Cl

Ba2 Cl

Ba2 Cl

Ba Cl2


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Chemical Bonds 33

Section 1 Stability in BondingA. Some elements combine chemically and no longer have the same ___________________ they

did before forming a compound.

B. A(n) _________________________ is composed of symbols and subscripts indicating the

number of atoms of an element in a compound.

C. Atoms form compounds when the compound is more _______________ than the separate atoms.

1. Noble gases are more __________________________ than other elements because they

have a complete outer energy level.

2. Elements that do not have full outer energy levels are more stable in __________________.

3. Atoms can lose, gain, or ______________ electrons to get a stable outer energy level.

4. A(n) ______________________ is the force that holds atoms together in a compound.

Section 2 Types of BondsA. A(n) ____________ is a charged particle because it has more or fewer electrons than protons.

1. When an atom ______________ an electron, it becomes a positively charged ion; a super-

script indicates the charge.

2. When an atom ______________ an electron, it becomes a negatively charged ion.

B. An ionic compound is held together by the ___________________—the force of attraction

between opposite charges of the ions.

1. The result of this bond is a(n) ________________ compound.

2. The sum of the charges on the ions in a unit of the compound is _____________.

C. __________________ are neutral particles formed as a result of sharing electrons.

1. A ______________________ is the force of attraction between atoms sharing electrons.

2. Atoms can form double or triple ______________ depending on whether they share two or

three pairs of electrons.

3. Electrons shared in a molecule are held _____________________ to the atom with the

larger nucleus.

Note-takingWorksheet

Chemical Bonds

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34 Chemical Bonds

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4. A(n) ______________ molecule has one end that is slightly negative and one end that is

slightly positive although the overall molecule is neutral.

5. In a(n) _________________ molecule, electrons are shared equally.

Section 3 Writing Formulas and Naming CompoundsA. Chemists use ________________ from the periodic table to write formulas for compounds.

B. A ________________________ is composed of two elements.

1. _________________________—how many electrons an atom has gained, lost, or shared to

become stable

2. Use oxidation numbers and their least common multiples to write _________________.

a. When writing formulas, remember that the compound is ________________.

b. A formula must have the correct number of positive and negative ions so

the charges ________________.

3. Use the name of the first element, the root name of the second element, and the suffix –ide

to write the _____________ of a binary ionic compound.

C. _______________________—positively or negatively charged, covalently bonded group

of atoms

1. The compound contains ______________ or more elements.

2. To write names, write the name of the _________________ ion first; then write the name

of the _________________ ion.

3. To write _________________, use the oxidation numbers, determine their least common

multiple, and put parentheses around the polyatomic ion before adding a subscript.

D. ________________—compound with water chemically attached to its ions

E. Name binary covalent compounds by using _________________ to indicate how many atoms

of each element are in the compound.

Note-taking Worksheet (continued)


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36 Chemical Bonds

Assessment

Assessment

Name Date Class

Chapter Test (continued)

Chemical Bonds 41

2. Which of the following is the correct formula for magnesium nitrate?a. MgNO3 b. Mg2NO3 c. Mg(NO3)2 d. Mg2(NO3)2

3. What is the charge of phosphate in K3PO4?a. 3– b. 1+ c. 5+ d. 7–

4. How many potassium atoms and how many oxygen atoms are there in a binary compound made from these two elements?a. one potassium and two oxygen c. one potassium and one oxygenb. two potassium and one oxygen d. three potassium and one oxygen

5. What is the correct name for K2SO4?a. potassium sulfide c. potassium sulfateb. potassium(II) sulfate d. potassium disulfide

6. What is the correct formula for magnesium oxide?a. MgO b. MgO2 c. Mg2O2 d. Mg2O

7. What is the name of the compound with the formula CaO?

8. What is the name of the compound with the formula MgCl2?

Skill: Concept MappingDirections: Identify, by writing in the appropriate column in the table, which of the terms listed below could belinked in a concept map to ionic bonds and which could be linked to covalent bonds.

ions positive ions molecules

nonpolar negative ions polar

Element/Polyatomic Ion Symbol Oxidation Number

Potassium K 1+

Magnesium Mg 2+

Oxygen O 2

Nitrate NO3 1

Sulfate SO4 2

Phosphate PO4 3

9. Ionic Bonds 10. Covalent Bonds

Skill: Using TablesDirections: Use the following table to answer questions 2 through 7.

Asse

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Chapter Test (continued)

42 Chemical Bonds

III. Applying ConceptsDirections: Use the rules for naming compounds and writing chemical formulas to complete the following items.

1. Write the names for the following compounds.

a. CaBr2

b. CuCl

c. MgS

2. Write the formula for each of the following compounds.

a. copper(I) sulfide

b. calcium chloride

c. calcium oxide

3. A lithium atom has three protons and three electrons. A fluorine atom has nine protons andnine electrons, with seven electrons in its outer energy level. Using a diagram of the two atoms,explain how lithium fluoride forms with ionic bonding between the lithium atom and the fluoride atom.

IV. Writing SkillsDirections: Answer the following questions using complete sentences.

1. Explain how to write the formula for a binary compound.

2. Explain the rules for naming a binary compound from its formula.

Assessment

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Transparency Activities

Chemical Bonds 43

Tran

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44 Chemical Bonds

Section FocusTransparency Activity11

Jigsaw puzzles can have hundreds—even thousands—of pieces. Tocomplete the puzzle, you need to infer how each piece fits together.Size, shape, and markings all give clues as to how the pieces should beplaced to make a picture.

Picking Up the Pieces

1. Where do the remaining pieces belong? How do you know?

2. How might a compound and its individual elements compare to a puzzle and its pieces?


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Chemical Bonds 45


This picture shows salt crystals on the Dead Sea shore. When a saltcrystal is pure, it is in the shape of a colorless cube. Impurities canmake salt appear to be different colors, like white or gray. Table salt isa compound of sodium and chlorine.

A Crystal Nature

1. Describe the appearance of the salt in the picture.

2. What happens to salt in water? How might you recover salt fromocean water?

3. How do people use salt?Tr

ansp

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46 Chemical Bonds


Why are these workers trying to keep the concrete wet rather thanletting it dry? Concrete doesn’t harden because it dries. It hardens byincorporating water into its molecular structure. If there’s not enoughwater, the concrete won’t harden properly, and it won’t be verydurable.

For Best Results, Add Water

1. How might construction be different in the desert compared to arainy, temperate region?

2. What would happen if a bag of dry concrete got a little damp?What if it got very wet?

3. When a new sidewalk is finally dry, where does the water go?


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Chemical Bonds 47

Teaching TransparencyActivity33 Common Oxidation

Numbers of Selected Groups

→ →

Chlo

rine

Cl

Sodi

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Na

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N

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Kr Xe Rn

Ar

Ne

Boro

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Alum

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13 Al

Galli

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a

Indi

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Thal

lium

81 Tl

Carb

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Silic

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Germ

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e

Tin

50 Sn Lead 82 Pb

Nitr

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Phos

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Arse

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Antim

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51 Sb

Bism

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83 Bi

Oxy

gen

8 O

Sulfu

r16 S

Sele

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34 Se

Tellu

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52 Te

Polo

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84 Po

Fluo

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Chlo

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17 Cl

Brom

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35 Br

Iodi

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Asta

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Hel

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Argo

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Rado

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Lith

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Pota

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Rubi

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Cesi

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Fran

cium

87 Fr

Bery

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4 Be

Mag

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g

Calc

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20 Ca

Stro

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Radi

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48 Chemical Bonds

Name Date Class

Teaching Transparency Activity (continued)

1. When does an ionic bond form between elements?

2. What is a covalent bond?

3. The formula for baking soda is NaHCO3. Name the elements in baking soda.

4. How many pairs of electrons are shared when hydrogen and oxygen unite to form a moleculeof water?

5. Using the oxidation numbers given on the transparency, write the formula for calcium chloride, a compound of calcium and chlorine.

6. Write the formula for barium (Ba2+) chlorate (ClO3–).

7. Name two pieces of information you can get from a dot diagram.


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Name Date Class

Chemical Bonds 49

AssessmentTransparency Activity

Directions: Carefully review the tables and answer the following questions.

Chemical Bonds

1. The compounds in Group A are different from the compounds inGroup B because only the compounds in Group A ___.A are gases at room temperatureB are used in preparing foodC contain a metal and a nonmetalD contain only two different elements

2. According to the chemical formula for lye, all of the following ele-ments are found in a lye molecule EXCEPT ___.F hydrogen H oxygenG nitrogen J sodium

3. According to the information contained in the tables, which compound has a total number of atoms greater than 10?A Baking soda C SugarB Methane D Vinegar

4. According to the tables, which compound has the LEAST numberof total atoms?F Ammonia H SaltG Carbon dioxide J Water

Group A

H2O

CO2

NH3

NaCl

CH4

Water

Carbon dioxide

Ammonia

Salt

Methane

Group B

Mg(OH)2

C12H22O11

NaOH

NaHCO3

C2H4O2

Epsom salts

Sugar

Lye

Baking soda

Vinegar

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ency

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Chemical Bonds - Putnam High School Freshmen Academy Science - Home