positive negativeton bn

covalent bond .'

'o 2.6 Essontial Coll Biology. 3ta. (S 2<XM Gariand Science)

Name

TeacherRegents Chemistry

-1-

f\" A. TTb ~*#fe»iTU * *** .Covalent Bolras

Definition:

Types of Covalent Bonds

A. Nonpolar Covalent;

-fi •ttb.

B. Polar Covalent

C. Coordinate Coyalent'

Properties of Covalent Bonds

-3-

WS Covalent Lewis Pot Structures

What is the duet rule? Which atom does this apply to?

What is the octet rule?

Draw the electron dot (Lewis) structures for each covalent molecule.

F2 , 02

H,S CO-

/' -

HCI

H

PCI, '" SiH,

BeC

Which molecules above are exceptions to the octet rule

-4-

t">j£'^

Name

Covalent bonding occurs when two or more nonmetals share electrons, attempting toAttain a stable octet of electrons at least part of the time. For example:

\f x\X

Note that hydrogenis content with 2,not 8, electrons, .

^g3%a^

Show how covalent bonding occurs In each of the following pairs of atoms. Atoms mayshare one, two or three pairs of electrons.

i. H + H .

2. F + F CF,)

3. O + O (0)

4. N + N (NJ

5, c + o (ccg

6- H +-0 (HO)

IF8766 39 Instructional Fair, inc.

-9-

iro '9

OTDH '

NDH 'II

'01 *£

"6 HO£HD '

'8

Form WS4.1.4A

BONDING

Name

Date Period

Covalent bonds are bonds formed by sharing electrons. The electrons of one atom are attractedto the protons of another, but neither atom pulls strongly enough to remove an electron from theother. Covalent bonds form when the electronegativity difference between the elements is lessthan 1.7 (see the Electronegativity table on the back of the Periodic Table) or when hydrogenbehaves like a metal. When a covalent bond forms., no valence electrons are transferred, rather,they are shared. If the electronegativity difference is zero, the electrons are shared equally andthe bond is nonpolar. If the electronegativity difference is greater than 0.4 but less than 1 .7, theelectrons are displaced towards the more electronegative element (nonmetal) and the bond ispolar. In a covalent bond, unpaired valence electrons pair up in such a way that the atomscomplete their outer shells.

Electron Dot Diagrams Showing UnpairedValence Electrons (NOTE: When bonding occurs, molecular orbitals form. Asa result, the two electrons that are normally paired in the lowest energy orbital move into separate orbitals)

Li- Be- - B - - C -

-N: - :

Pairing Electrons:

Nonpolar Covalent Bond: Cl° + Cl° -+ C12 : Cl. + ' Cl: : Cl: Cl

Polar Covalent Bond: H+ + Cl" -> HC1 H. + -Cl : H:C1

Based on your understanding of covalent bonds, answer the questions below.

1. Draw electron dot diagrams for hydrogen and oxygen.

2. Draw electron dot diagrams showing the pairing of electrons to form water from hydrogen and oxygen. All outershells should be complete.

3. Are the bonds in water polar or nonpolar. How do you know?

Evan P. Silberstein, 2002

.... ,, - 4.. u-'y *4.u « i i V v r -.JAIM: How is the shape of the.molecQleirelatedito the?group number?4vr " *V *•*, tv»ji - ° rfM*J*flf**% *-?*

Elements fromGroups

Arrangement ofelectrons

Name ofmolecular

shape

Symmetrical orasymmetrical

Polar ornonpolar

xamples/generalformula

Name Date

Aim: How does the shape of a molecule effect its polarity?

Chemistry Regents

BeH2

C02

Symmetrical molecules

H— Be— H

H

•••MH-'-C-rH

IH

FtB

/ vF F

HBr

H2S

Asymmetrical molecules

H—Br

H

ff

CONCLUSION:

Name

Using VSEPR Theory, name and sketch the shape of the following molecules.

,- N2 .

2. H,0

7, HF

8. CH3OH

3. CO, 9, H2S

4". NK 10,

5. CH, 11. CHCL

6. SO, 12. CX

Chemistry IF8766 41 ©Instructional Fair, Inc.

-9-

Name

c .Determine whether the following molecules are polar or nonpoiar.

1. N2

2. H20

3. C02

4. NH3

*5.' CH4

6. S03

Chemistry IF3766 4

7. HF

.»

8. ChLOHo

9. H2S

10. I2

11. CHC!3

12. 02

2 ©Instructional Fair. Inc.

f

isSf1;f1

ti

E

A

\

r

!

i

?AcJ 1,<^

f 3,t

1 6-

1 8l

! n.i| 14 -

15i

16

17

^ ^

. che

Form WS4 . 1 . 6A

BONDING

Name

Date Period

To determine if a compound is polar, you must consider the electronegativity differencewithin each bond and the three dimensional shape of the compound. If the electronegativitydifference is greater than 1.7 or close to zero, the compound is not polar. Electronegativitydifferences above 1.7 are found in ionic compounds. Electronegativity differences aroundzero are found in molecules with nonpolar bonds. Electronegativity differences between 0.4and 1.7 are found in molecules with polar bonds. These molecules can be polar or nonpolardepending on their shapes. Molecules with polar bonds distributed symmetrically arenonpolar. Asymmetrical molecules with polar bonds are polar. Water is polar. An imaginaryline can be drawn through a water molecule separating the positive pole from the negativepole. This is because the charges are distributed asymmetrically. Carbon dioxide is nonpolar f ~because the electronegative oxygens are distributed symmetrically around the carbon. ?at.er.uS ,polar' because Jle charges are

d i s t r i b u t e d a s y m m e t r i c a l l y . The(0—C—O) electropositive hydrogens are attached to

oxygen's two unpaired electrons..

Determine if each of the compounds listed below, IONIC, POLAR, or NONPOLAR asfollows: [1] determine the types of bonds. [2] draw electron dot diagrams to determine the shape.

Compound

HC1

CH4

C12

KBr

NH3

Type ofBond:IONIC,

POLAR, orNONPOLAR

Electron DotDiagram

Type ofCompound: IONIC,POLAR, orNONPOLAR

Compound

CC14

CH3C1

N2

H2S

NaBr

Type ofBond:IONIC,

POLAR, orNONPOLAR

Electron DotDiagram

Type ofCompound: IONIC,POLAR, orNONPOLAR

Evan P. Silberstein, 2007

-11-

Name

Ms. Tintella

Covalent Bonding

Practice 1

Date

Regents Chemistry

1. A molecular compound is formed when a chemicalreaction occurs between atoms of

1) chlorine and sodium2) chlorine and yttrium3) oxygen and hydrogen4) oxygen and magnesium

2. What is the total number of electron pairs sharedbetween the two atoms in an Ch molecule?

1) >) 2 3) 6 4) 4

3. What is the total number of electrons shared in adouble covalent bond?

1) 1 2) 2 3) 3 4) 4

4. Which compound has both ionic and covalentbonding?

1) CaCOs3) CH3OH

2) CHiCb4)

5. The nitrogen atoms in a molecule of N2 share atotal of

1) one pair of electrons2) one pair of protons3) three pairs of electrons4) three pairs of protons

6. Which formula represents a molecular compound?

1) HI 2) KI 3) KC1 4) LiCl

7. Which formula represents a molecular compound?

1) Kr 2) LiOH3) N2O4 4) Nal

8. Which characteristic is a property of molecularsubstances?

1) good heat conductivity2) good electrical conductivity3) low melting point4) high melting point

9. What is the maximum number of covalent bondsthat a carbon atom can form?

1) 1 2) 2 3) 3 4) 4

10. In the diagram of an ammonium ion to the right.why is bond A considered to be a coordinatecovalent bond?

H ' N S HX o

H

A

1) Hydrogen provides a pair of electrons to beshared with nitrogen.

2) Nitrogen provides a pair of electrons to beshared with hydrogen.

3) Hydrogen transfers a pair of electrons to thenitrogen.

4) Nitrogen transfers a pair of electrons tohydrogen.

11. Which molecule has a nonpolar covalent bond?

1) H-H 2) H^Ns,H

H

3) H-°-H 4) H-CI

12. The chemical bond between which two atoms ismost polar?

1) C-N 2) H-H 3) S-C1 4) Si-0

Covalent Bonding

13. Which formula represents a nonpolar moleculecontaining polar covalent bonds?

1) H20 2) CC14 3) NHa 4) Hi

14. The bonds between hydrogen and oxygen in awater molecule are classified as

1) polar covalent3) ionic

2) nonpolar covalent4) metallic

15. Which type of molecule is CF4?

1) polar, with a symmetrical distribution ofcharge

2) polar, with an asymmetrical distribution ofcharge

3) nonpolar, with a symmetrical distribution ofcharge

4) nonpolar, with an asymmetrical distributionof charge

16. Given the formula representing a molecule:

H-C-C-H

The molecule is

1) symmetrical and polar2) symmetrical and nonpolar3) asymmetrical and polar4) asymmetrical and nonpolar

17. Which formula represents a nonpolar molecule?

1) HC1 2) H20 3) NH3 4) CH4

18. Why is a molecule of CCh nonpolar even thoughthe bonds between the carbon atom and theoxygen atoms are polar?

1) The shape of the CCh molecule issymmetrical.

2) The shape of the CCh molecule isasymmetrical.

3) The CCh molecule has a deficiency ofelectrons.

4) The C02 molecule has an excess ofelectrons.

19. Which formulas represent two polar molecules?

1) CChandHCl 2) CCh and CH4

3) H20 and HC1 4) H20 and CH4

20. Which formula represents a polar molecule?

1) Br2 2) CCh 3) CH4 4) NH3

BAN DIHYDROGEN MONOXIDE!Dihydrog'en monoxide is colorless, odorless, tasteless, and kills uncounted thousands of

people every year. Most of these deaths are caused by accidental inhalation of DHMO, but thedangers of dihydrogen monoxide do not end there.

Prolonged exposure to its solid form causes severe tissue damage. Symptoms of DHMOingestion can include excessive sweating and urination, and possibly a bloated feeling, nausea,vomiting and body electrolyte imbalance. For those who have become dependent, DHMOwithdrawal means certain death.

Dihydrogen monoxide:is also known as hydroxl acid, and is the major component of acid rain.contributes to the "greenhouse effect."may cause severe burns.contributes to the erosion of our natural landscape.

• • accelerates corrosion and rusting of many metals.may cause electrical failures and decreased effectiveness of automobilebrakes.

• has been found in excised tumors of terminal cancer patients.

Contamination is reaching epidemic proportions!

Quantities of dihydrogen monoxide have been found in almost every stream, lake, andreservoir in America today. But the pollution is global, and the contaminant has even been foundin Antarctic ice. DHMO has caused millions of dollars of property damage in the midwest, andrecently California.

Despite the danger, dihydrogen monoxide is often used:• as an industrial solvent and coolant.• in nuclear power plants.• in the production of styrofoam.• as a fire retardant.• in many forms of cruel animal research.• in the distribution of pesticides.• as an additive in certain "junk-foods" and other food products.

Even after washing, produce remains contaminated by this chemical.

Companies dump waste DHMO into rivers and the ocean, and nothing can be done tostop them because this practice is still legal. The impact on wildlife is extreme, and we cannotafford to ignore it any longer!

The American government has refused to ban the production, distribution, or fee of thisdamaging chemical due to its "importance to the economic health of this nation." In fact, thenavy and other military organizations are conducting experiments with DHMO. and designingmulti-billion dollar devices to control and utilize it during warfare situations. Hundreds ofmilitary research facilities receive tons of it through a highly sophisticated undergrounddistribution network. Many store large quantities for later use.

-12-

Name' Date Chemistry Regents

AIM: Writing chemical formulas- for molecular compounds.

Guidelines:

Problems:

1) Nitrogen trifluoride

2) Carbon monoxide

3) carbon tetrafluoride

'%

4) tetraphorous decaoxide

5) sulfur hexafhioride

6) dihydrogen monoxide

7) dinitrogentetrahydride

8) nitrogen trihydride

9) nitrogen monoxide

10) Dinitrogen monoxide

11) sulfur dioxide

-13-

"Naming Chemical Compounds #1

Directions: Write each compound in the space provided. ' : '

1.

2.

3.

4.

5.

6.

7.

Sodium sulfide

Magnesium chloride

Ammonium fluoride

Sodium acetate

Silver bromide

Calcium oxide

Potassium oxide

9.

10.

Calcium nitrate

Potassium phosphate

11. Potassium hydroxide

12. Magnesium chlorate

-14-

14.

15.

Carbon monoxide

Sulfur dioxide

16. Iron(III) nitrate

17.

18.

Carbon dioxide

Sulfur trioxide

19. Lead(II) oxide

20. Lead(IV) oxide

21. Sb(OH);

Sb(OH);

23.

24. CoS04

-15-

: Form WS4.3.4A

BONDING

Name

Date Period

Nonmetals are two-faced elements! Although they normally have negativeoxidation states, nonmetals can behave like metals and have positive oxidation'states. As a result, two nonmetals can combine to form compounds. When two -•' Why arenonmetals combine, they form covalent bonds. The nonmetal with the lower / WQU soelectronegativity behaves like a metal and has a positive oxidation state. In \negative?carbon dioxide (CO2), the carbon behave like a metal while the oxygen behaveslike a nonmetal. The rnetal is written first in the name and the formula. Thename of the metal is the same as the name of the element (C = carbon, C1"4 =carbon). If there is more than one atom of the metal, the number of atoms isindicated with a prefix. (See the list of prefixes below.) The nonmetal is writtenlast in the name and formula..The name of the nonmetal is the same as the nameof the element minus the final syllable or two, plus IDE (O — oxygen, O~2 =oxide).The number of nonmetal atoms is indicated with a prefix (even whenthere is only one). Writing formulas for these compounds is easy; because theprefix tells the subscript

Why areyou so

positive?

ExamplesC1203 = dichlorine trioxidesilicon tetrafluoride = SiF4

Name the following binary covalent compounds.

1. BrCl5 . . . . ________

2. S03

3- P203

4. As3P5 . . . .

5- IF7

6. SeS3 _____—__-_____-———.

Number of Atoms

10

Prefix

mono

di

tetra

penta

hexa

hepta

octa

nona

deca

7. SO2 .

S. CO .

9. SBr5

10. N2O5

EvanP.Silberstein, 2002

-16-

CMijerftisfcrcf: Form W S 4 . 3 . 2

BONDING

r '\c lxi©T:S' C/(§)TU7°©urv:^^

Write the correct name of the compound onformulas listed below.

1. Ca,(POJ,

2. Pbl,

3. AKHSO.K

4. F e ( O H ) ?

O . k_^ J_ j

O . v^S*?oLJj

/ , .1.1 ". M-.x-* v-J"1

8. BaS04

9. A1P

10. NH,NOq

11. Cu,O

12. Hcr,COq

13. Acr,C,0,

V 14. C u ( S C N ) ,

15. LiOH

16. AQ,S

17 . Rb,N

18. FeS04

19. ZnBr?

20. Pb(CrOJ,

21. MnCr907

22 . SrHo

23. Sr (CH,COO)9

24. cs,

25. MnO,

26. Kr,P

27 Na S OM

28. BaS

29. H^PO-^

. 30. FrMn04

Name

Date Period

the space provided for each of the

31 . KC1

32 . Mgl?

33 . MaHSO4

34. Hq^(P0 4 } ?

35. Ni(C100?

36. CdF?

37. SnS

38 . C0?

39. NaCl

40 . S b ( N O ? ) ^

41. S n ( C O 3 ) 2

42. KHS04

43. Asl,

44. NH4OH

45. SiCl4

46. NHjClO^

47 ClTo ( 0^0* 1

48. NiF2

49. SO?

50. BiCO?

51. As205

52. CdO?

53. (NH 4 ) 2Cr 20 7

^d. Ten n•-> ^t . £\v^j,v^^

^ R ^n»J «J - OVJ^

56. Z n ( N O ^ ) 9

57. CqP4

58. Sn07

59. NH4Br

60 . Na?0

Evan P. Silberstein, 2002

-17-

Name

.When nonmetals chernicaily bond they do so by sharing electrons. The bond is called a_3vale'ht bond. When an active metal and a nonmetal bond, the active metal transfers

^one or more electrons to the nonmetal. This bond is called an ionic bond, ioniccompounds (except for bases) are also called salts,

Classify the following compounds as ionic or covaient,

1. CaCl

2. CO,

3, H20

4. BaSO

5. CX

6. NaF

7. Na2C03

8, Se

~ . S03

10. LiBr

11. MgO

12. C2H

13. HCI

14. N2

15. NaOH

16. N02

17. A!PO4

18. Fed,

19. P205

20, N203

21. H

22.

23, Kl-

24. P4

25.

26, Nad

Draw an electron shell diagram of theionic compound calcium oxide, CaO,

Draw an electron shell diagram of thecovaient compound methane, C\i4.

Biology IF8765 13 ©Instructional Fair, Inc.

f: Form Ls4 . lA Chemical Bonds

BONDING Page 2

. Answer the questions below by circling the number of the correct response

1. Barium combines by (1) gaining two electrons, (2) losing twoelectrons, (3) sharing two electrons, (4) sharing 3 electrons.

2. Which of the following is the correct electron dot diagram fornitrogen?

(1) (S) (3) (4)

3. In water, the bond between hydrogen and oxygen is (1} ionic,(2) polar covalent, (3) nonpolar covalent, (4} nonpolarnoncovalent.

, 4. Which of the following occurs during covalent bonding?(1) Electrons are lost. (2) Electrons are gained, (3) Valenceelectrons fall from the excited state to the ground state.(4) Unpaired electrons form pairs.

5. Which of the following is an example of a substance with anonpolar covalent bond? (1JHCI (2) CI2 (3) HC!0Z (4) NaCI

6. The electronegativity of sulfur is (1) 16, (2)239, (3) 2.6, (4)32.

7. Which of the following elements has the highest electronegativity?(1) fluorine (2) chlorine (3) barium (4) hydrogen

8. The formula for magnesium fluoride is MgF2. The best explanationfor this fact is that when they combine (1) each of two magnesiumatoms lose an electron and a fluorine atom gains two, (2} amagnesium atom loses two electrons and each of two fluorineatoms gains one, (3) a magnesium atom shares two electrons withtwo fluorine atoms, (4) each of two magnesium atoms share anelectron with a fluorine atom.

9. When calcium combines, it usually (1) loses two electrons,(2) gains six electrons, (3) shares two electrons, (4) shares sixelectrons.

10. What is the maximum number of atoms carbon can combine withat once? (1)1 (2)2 (3)3 (4)4

Evan P. Silberstein, 2002

-19-

Name Date Chemistry Regents

Drawing Lewis Diagrams for Ionic & Covalent Bonds

Chemicalformula

F2

HC1

K2S

H2O

NH3

Compoundname

Nitrogen

Carbondioxide

Bariumchloride

Oxygen

Type of Bond Lewis Dot Diagram

-20-

Name Date Chemistry Regents

Bonding Summary

BONDING:

: Form WS4 . 4 . 1A

BONDING

Name

Date Period

C

Until about 5,000 B.C., people made tools and implements fromstone. Around 5,000 B.C., it was probably noticed that meltedcopper ran from green ore in a pottery kiln. Around that sametime, gold was discovered and used for decorations. Metalsbecame prized for jewelry because of their luster. By 3500 B.C.,humankind discovered that melting copper together with tinformed a harder metal, heralding the start of the Bronze Age.Around 1500 B.C., technology leaptforward once again when thehotter ovens of that age enabled the extraction of iron, an evenharder and more abundant metal, from its ore. In many ways, weare still in the Iron Age. Modern civilization depends on alloysof iron for its bridges, skyscrapers, and automobiles. The physicalproperties of metals that make them so useful are due to metallicbonding which makes them both strong and flexible.

Read the description of metallic bonding below, and answer the questions that follow based on yourknowledge of chemistry and metals in particular.

1. Why are metallic bonds both strong and flexible?

2. Why are metals able to conduct both heat and electricity

well?

Metallic BondingMetals have low ionization energies. This means theyhold onto electrons loosely. As a result, in a metalcrystal, the valence electrons move easily and do notbelong to any single atom. Since the atoms in thecrystal do not hold on to their own valence electrons,they become like cations in a sea of mobile electrons.The attraction between the cations and the electronsholds the metal crystal together.

Group 1 metal Group 2 metal

3. The valence electrons of metals jump easily to a higher energy orbital when light shines on them. Then they

fall emitting the excess energy as light. Which property of metals is explained by this?

© Evan P. Silberstein, 2002

-22-

Form Ls4 .4A

BONDING

Name

Date Period

Examine bonds that are not chemical bonds

Metallic bondsif Formation

•£? in metals, electrons are easily lost or transferred•fr the electrons in metallic substances are not always associated with any particular atomtV as a result, the particles of a metal are usually positive ions surrounded by mobile electrons to which they are

attracted-&• Properties

*& strong bonds result in high melting points•£? mobile electrons result in luster, flexibility, and good conductivity

Intermolecular attractions - forces of attraction between particles that are not chemically bonded^r Dipole-dipole attraction

& Dipole - a polar molecule, or a molecule with an asymmetric, or unequal, distribution of charge causing one endof the molecule to be positive while the other is negative

-& Definition - force of attraction between the positive end of one dipole and the negative end of another& Hydrogen bonding

-& Definition - an intermolecular force linking an electropositive hydrogen that is covalently bonded to a smallelectronegative element such as oxygen, nitrogen, or fluorine, to another electronegative element of the same oranother molecule

0 Hydrogen

© Oxygen

Evidence - uncharacteristically high boiling point of water

Boiling Points of Related Compounds100

BLTe

-100

20 40 60 80 100Atomic Mass

120 140

-23-

Definition:

Intermolecular Forces

Type Definition Example Strength

Dipoles

HydrogenBonding

Dispersion Forces(van der walls)

Molecule-IonAttraction

: Form W S 4 . 4 . 3 A

BONDING

Name

Date Period

Tics

Pure substances can be held together by ionic bonds, covalentbonds, metallic bonds, or intermolecular forces. Most materialsare mixtures, and are held together by a mixture of these forces.Figuring out what holds things together takes some seriousanalysis. If the substance is pure and you know the formula, youcan figure out the electro negativity difference. If it is 1.7 orgreater, than it is ionic. All ionic substances are crystalline solids.Diamonds are also crystalline solids, but they are made of purecarbon. What does that tell you about the electronegativitydifference? Electro negativity differences below 1.7 are covalent.Large crystals such as diamond or sand (Si02) that have anetwork of covalent bonds are called macromolecules ornetwork solids. Smaller compounds containing covalent bondsare called molecules. The molecules of a substance may beattracted to each other to form solids or liquids byintermolecular forces. These are often calledmolecular compounds. Molecular solids are softerthan covalent solids (network solids) and ionicsolids, because intermolecular forces are weaker thanchemical bonds. The flow chart to the right showsone way of classifying the types offerees that holdsubstances together.

Once you have determined that a material is heldtogether by intermolecular forces, this can be furtherrefined. If the substance is polar, it is held togetherby dipole-dipole attractions. If the polar substancecontains hydrogen atoms attached to either oxygen,nitrogen, or fluorine atoms, it forms especially strongdipole-dipole attractions called a hydrogen bonds.Hydrogen bonds are responsible for the threedimensional shapes of many proteins because thelarge protein molecule folds in such a way thathydrogens in one part of the molecule are close tooxygens or nitrogens in another part of the molecule. -

NEXT PAGE

/Tm stuck up here,be ionic bonding, covalentbonding, metallic bonding,or intermolecular forces, I

•ydonM know, but I'm stuck.

-29-

Form WS4 . 4 . 3A The Ties that Bind

BONDING Page 2

Below are some familiar materials. Based on the reading and your knowledge of chemistry, state whethersamples of these materials are held together by ionic bonds, covalent bonds., metallic bonds, dipole-dipoleattractions, hydrogen bonds, or other intermodular forces.

1. Water [H20(e)] ^^_^^^_^_^_^_______^^__^_^^^____

2. Table sugar [C12H220U(.?)] . . .

3. Table salt [NaCl(s)]

4. Iron railing [Fe(^)]

5. Liquid oxygen [0200]

6. Diamond [C(j)]

7. Salt substitute [KI{»] ______^_^____

8. Alcohol [CH3CH2OH(C)] ^_^__^_____

9. Chlorine [Cl2fe)] _^

10. Gasoline [C8H18(0)]

11. Gold [AuO)] ^^^_^_^___

12. Rust [Fe203(»] _^ ^^_^^____^^___

13. Tarnish [Ag2S(»]

14. Tooth enamel [Ca3(P04)2(5)] .. _

15. Copper wire [Cu(,y)] __

© Evan P. Silberstein, 2002

: Form WS4.4.2A

BONDING

Name

Date Period

Complete the observations below and answer the questions that follow.Fill a 50 mL beaker most of the way with water.

* Continue adding water one drop at a timenote how high the water can go without spilling.

1. Describe what happened when you kept adding water to analready full beaker? Draw a picture of how it looked in the

space to the ripcht. Why does this happen?

of hydrogen and members of the oxygen family. f ,-> T n • i. £ r-. i L _j ^ ^ 1i Boiling P0|rts °f Related Compounds |

a. What is the electronegativity difference in each 1QQ ~r^~ "f"

compound?

o

b. How can the differences in the boiling points be £

explained?-50

-100

H.Te

0 20 40 60 80 100 120 140Atomic Mass

3. What holds many solids and liquids together?

Evan P. Silberstein, 2002

-31-

: Form Ls4 .4A

BONDING

Metallic Bonds and intermolecular Forces

Page 2

Answer the questions below by circling the number of the correct response

1. Which substance will conduct electricity in both the solid phaseand the liquid phase?(1}AgCi . (2)H2

(3)Ag (4)HCI

2. Hydrogen bonds are strongest between molecules of(1)HBr(g) (3) HF(g)(2)HI(g) (4)HCI(g)

3. Which molecule is a dipole?(1)H2 (3)CH4

(2)N2 (4)HCI

4. The strongest hydrogen bonds are formed between molecules of(1)H2Te (3)H20(2) H2Se (4) HZS

5. What type of bonds are present in a strip of magnesium ribbon?1 covalent 3 metallic2 ionic 4vanderWaals

6. Hydrogen bonds are most likely to exist between molecules ofd)H2 (3) HI(2)CH4 (4)H20

7. Which substance, in the solid state, is the best conductor ofelectricity?(1)Ag (3) Nad(2)I2 (4)C02

8. Which is the predominate type of attraction between molecules ofHF in the liquid state?1 hydrogen bonding 3 ionic bonding2 eiectrovalent bonding 4 covalent bonding

9, Which substance exists as a metallic crystals(1)Ar (3)Si02

(2) Au (4) C02

10. Mobile electrons are a distinguishing characteristic of1 an ionic bond 3 a metallic bond2 an eiectrovalent bond 4 a covalent bond

11. Which kinds of bonds are found in a sample of H20(s)?1 hydrogen bonds, only2 covalent bonds, only3 both ionic and hydrogen bonds4 both covalent and hydrogen bonds

12. Which substance is made up of molecules that are dipoles?[1) N2 (3) CH,(2) H20 (4) C02

13. Which element consists of positive ions immersed in a "sea" ofmobile electrons.?1 sulfur 3 calcium2 nitrogen ' 4 chlorine

EvanP. Silberstein,2002

-32-

: Form WS4 . 3 . 5A

BONDING

Name

Date Period

it all T

Below is a flow chart showing the steps to follow when naming a compound from the formula. Following the flowchart will enable you to determine when to use the stock system, when to use a set of prefixes, and when to lookup the names of polyatomic ions in Table E.

Use procedures for.{binary tonic compound,I -,faut'use;name ofI . polyatomic ion foi

rnetai.or nonmsial

Biftary Cnyaient

Usepiefixes;

Metal present? I

Does metal formmore than one cation?

lore than one oxidation state)

x Use the element 'name for the cation. .

Stgckjjyjtem '•* Determine the charge offfhe cations; Use a romanBurner at after the element- name'for the cation.

The compounds below are of several different types. Use the flow chart to determine the naming system touse and name each compound shown below.

1. FeCNO^a .

2. Na2S2O3 . .

3. P205

4. BaBr2

5. Mn2(Cr2O7)7

6. CaCL, . . . .

7. (NH4)2S ..

8. CuF

9. Br2O . . .

10. HgS04 .

11. A12O3 ..

12. SC16 . . .

13. IF7 ....

14. Cr(C03)3

15. KNO2 ..

16. AuP . . .

Evan P. Silberstein, 2002

-33-

Is defined as the force of attractionfor electrons between nuclei.

Tt can be:

Metallic

T

Covalent

Which is a "sea ofmobile electrons".

Which is a transferof electrons.

Which is a sharingof electrons, It can be:

A special kind is:

Ex: Ca (s) and Au (s)

* A MetalEx: NaCl and KF

• A Metal &Nonmetal

Coordinate Covalent

Which is a covalent bond in whichone atom donates both electrons .

Which is an equalsharina of electrons

Ex:Formed in polyatomicons.

Which is an unequalsharing of electrons

Ex: H2, N2• Two same

nonmetals

Ex: H20 , NH3• Two different

nonmetals

Name Bonding Practice DateMs. Tintella Regents Chemistry

1. Which formula represents a molecule having anonpolar covalent bond?

A) H B) HI 1

H _ C _ N _ H H-C-Hi 1 1

H H HC) H H D) H

I I 1H-C-C-H H-C-OH

1 1 1H H H

2. The chemical bond between which two atoms ismost polar?

A) ON B) H-H C) S-C1 D) Si-O

3. Which formula represents a nonpolar moleculecontaining polar covalent bonds?

A) H20 B) CCU C) NH3 D) H2

4. The bonds between hydrogen and oxygen in awater molecule are classified as

A) polar covalent B) nonpolar covalentC) ionic D) metallic

5. Which type of molecule is CF4?

A) polar, with a symmetrical distribution ofcharge

B) polar, with an asymmetrical distribution ofcharge

C) nonpolar, with a symmetrical distribution ofcharge

D) nonpolar, with an asymmetrical distributionof charge

6. Which compound has molecules that form thestrongest hydrogen bonds?

A) HI B) HBr C) HF D) HC1

7. Which electron-dot diagram represents a moleculethat has a polar covalent bond?

A) HJCI :C) ** xx

V *-M V*

B)

D). . X X

8. Which molecule contains a polar covalent bond?

A) xx ..' B")} six-i: j Hm

XX - • '

0 H . x N r - H D) - : N * N S• x

H9. Given the formula representing a molecule:

H-C=C-H

The molecule is

A) symmetrical and polarB) symmetrical and nonpolarC) asymmetrical and polarD) asymmetrical and nonpolar

10. Which electron-dot structure represents anon-polar molecule?

A)

C)

D)

H:CI :

: H

B) H

H: C: H• «

HH

H:O:* *

H

11. Two fluorine atoms are held together by acovalent bond. Which statement correctlydescribes this bond?

A) It is polar and forms a polar molecule.B) It is polar and forms a nonpolar molecule.C) It is nonpolar and forms a polar molecule.D) It is nonpolar and forms a nonpolar

molecule.

12. Given a formula for oxygen:

:o=6:What is the total number of electrons sharedbetween the atoms represented in this formula?

A) 1 B) 2 C) 8 D) 4

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Bonding Practice

13. What is the total number of pairs of electronsshared in a molecule of K2?

A) one pairC) three pairs

B) two pairsD) four pairs

14. What is the total number of electrons shared in thebonds between the two carbon atoms in a themolecule shown below?

H-C=C-H

A) 6 B) 2 C) 3 D) 8

15. Which compound contains only covalent bonds?

A) NaOH B) Ba(OH)2

C) Ca(OH)2 D) CH3OH

16. Which pair of atoms is held together by acovalent bond?

A) HC1C) NaCl

B) LiClD) KC1

17. Which compound contains both ionic andcovalent bonds?

A) HCl(g)C) NH4Cl(s) D)

NaCl(s)

18. Which is the correct electron-dot formula for ahydrogen molecule at STP?

A) H- B) H: C) H-H D) H-.H

19. Which characteristic is a property of molecularsubstances?

A) good heat conductivityB) good electrical conductivityC) low melting pointD) high melting point

•*20. In the diagram of an ammonium ion to the right,

why is bond A considered to be a coordinatecovalent bond?

H

X o

H

bond A

A) Hydrogen provides a pair of electrons to beshared with nitrogen.

B) Nitrogen provides a pair of electrons to beshared with hydrogen.

C) Hydrogen transfers a pair of electrons to thenitrogen.

D) Nitrogen transfers a pair of electrons tohydrogen.

-36-

Name Bonding Practice Date

Ms. Tintella Regents Chemistry

Base your answer to questions 1 through 3 on the table below.

Physical Properties of Four Gases

Name of Gas

Molecular Structure

Boiling Point (K) at 1 Atm

Density (g/L) at STP

hydrogen

H-H

20.

0.0899

hydrogenchloride

H-Cl

138

1.64

hydrogenbromide

H-Br

207

?

hydrogeniodide

H-l

237

5.66

1. Explain, in terms of molecular polarity, why hydrogen chloride is more soluble than hydrogen inwater under the same conditions of temperature and pressure.

2. Explain, in terms of intennolecular forces, why hydrogen has a lower boiling point thanhydrogen bromide.

3. Explain, in terms of electronegativity difference, why the bond in H-Cl is more polar than thebond in H—I.

4. Draw a Lewis electron-dot diagram for a molecule of phosphorus trichloride, PCI;

Base your answer to questions 5 and 6 on the balanced equation below.

2Na(s) + C12 -> 2NaCl(s)

5. Draw a Lewis electron-dot diagram for a molecule of chlorine, Cla-

6. Explain, in terms of electrons, why the bonding in NaCl is ionic.

-37-

Bonding Practice

7. Base your answer to the following question on the information below.

Each molecule listed below is formed by sharing electrons between atoms when the atomswithin the molecule are bonded together.

Molecule^: Cl2Molecule B: CCU Molecule C:

Explain why CC14 is classified as a nonpolar molecule.

Bromine is the only liquid nonmetallic element at room temperature. It is a heavy,mobile, reddish-brown liquid, volatilizing readily at room temperature to a redvapor with a strong disagreeable odor, resembling chlorine, and having a veryirritating effect on the eyes and throat; it is readily soluble in water or carbondisulfide, forming a red solution, is less active than chlorine but more so thaniodine; it unites readily with many elements and has a bleaching action; whenspilled on the skin it produces painful sores. It presents a serious health hazard, andmaximum safety precautions should be taken when handling it.

a Draw the electron-dot diagram of a molecule of bromine,b Why does bromine have properties resembling chlorine?

9. a) Draw the structural formula for HzO.b) Is this molecule polar or nonpolar? Explain your answer.

10. The natural gas delivered to consumers in the U. S. is about 95% methane (CH*, molecularweight 16 g/mol) with the remainder being mostly ethane, propane, and carbon dioxide.

Draw the Lewis electron-dot structure for a molecule of methane.

-38-

Bonding

What will students know and be able to do by the end of this instructional unit?1. Define and recognize:

a. Asymmetry f. Metallic Bondb. Chemical Bond g. Moleculec. CovalentBond h. Nonpolard. Intermolecular Forces of i. Polar

Attraction j. Polyatomic Ione. Ionic Bond k. Symmetry

2. Compare Ionic & molecular compounds3. Explain properties in terms of their corresponding bond types4. Interpret and draw lewis dot diagrams5. Assess polarity of a bond by using their elements electronegativity values6. Use the type of element to predict the polarity of the bond7. Differentiate between intermolecular forces8. Identify and differentiate polar and nonpolar molecules9. Apply "like-dissolves-like" to real world applications10. Identify the effects of intermolecular forces on physical properties and behavior11. In terms of intermolecular forces, explain vapor pressure, evaporation rate and phase

changes12. Interpret VP curves in terms of boiling points, evaporation, intermolecular forces, and

relative vapor pressure13. Explain colligative properties of solutes on water's boiling point, freezing point and

vapor pressure

Key Subject Competencies

• Explain energy changes associated with forming chemical bonds.« Describe the octet rule and how it relates to chemical bonding.• Describe what a noble gas configuration is and determine the n.g.c. for different

elements.• Explain how ionic bonds form and the properties caused by them (ionic substances).• Explain how covalent bonds form and the properties caused by them (network-covalent,

molecular-covalent substances).• Use the electronegativity difference between 2 elements to determine a compound's bond

type.e Explain how metallic bonds form and the properties caused by them.• Use element types (metal + nonmetal; only nonmetals; only metals) to determine what

bond type is present in a substance.• Describe Avhat polyatomic ions are and how to draw them in compounds.• Draw bond types (ionic or covalent) using Lewis Structures.• Explain how a substance (metallic or aqueous/melted ionic) is able to conduct electricity.

Explain why a substance (solid ionic or molecular or network) is NOT able to conductelectricity.

-39-

Bonding

• Explain and draw the difference between a single-covalent, double-covalent, and a triple-covalent bond.

• Determine and describe what it means for a bond to be a polar bond or a nonpolar bond,using charge symmetry.

• Determine and describe what it means for a molecule to be polar molecule or a nonpolarmolecule, using charge symmetry.

e Describe what an intermolecular force of attraction is and how they affect properties suchas solubility, melting point temperature, and boiling point temperature.

• Prioritize the types of intermolecular forces of attraction based on their strengths ofattraction between molecules

Vocabulary• Anion• Ion• Octet Rule• Asymmetrical Molecule• Ionic Bond• Polar Covalent Bond• Cation• Ion-Molecule• Symmetrical Molecule• Chemical Bond• Lewis Dot Diagram• Triple Covalent Bond• Covalent Bond• Metallic Bond• Van der Waal's Forces• Crystal Lattice Molecule• Dipole-Dipole• Multiple Covalent Bond• Hydrogen Bond• Nonpolar Covalent Bond• Intermolecular Forces• Octet

-40-

Name Date Class

Cova lent Compounds Lab#•ft

fir

E iectronegativity is a scale^used to determine an atom's attractionfor an electron in the bonding process. Differences in -

electronegativities are used to predict whether the bond is purecovaient, polar covaient, or ionic. Molecules in which theelectronegativity difference is zero are considered to be purecovaient. Those molecules that exhibit an electronegativity differenceof more than zero but less than 1.7 are classified as polar covaient.Ionic crystals exist in those systems that have an.electronegativitydifference of more than 1.7. .

The structures used to. show the bonding in covaient moleculesare called Lewis structures. When bonding, atoms tend to achieve anobie gas configuration. By sharing electrons, individual'atoms can

'complete the outer energy level. In a covaient bond, 3n octet ofelectrons is formed around each atom (except hydrogen.) . •

•i.To study covaient molecules, chemists find the use of models

helpful. Colored wooden or plastic balls are used to represent'atoms.These balls have holes drilled in them according to the number ofcovaient bonds they will form. The holes are bored at angles thatapproximate the accepted bond angles.

Sticks and springs are used to represent bonds. Single bonds areshown with sticks, while double and triple bonds are shown with twosprings and tKree spring's; respectively. While the sizes of the atomsare not proportionately correct, the models are useful to represent • -.the arrangement of the atoms according to their bond angles.'

ProblemHow can we determine thetype of bonds in a com-pound and draw andconstruct models of mole-cuies?

Safety Precautions

Objectives

• Construct models'to showthe shapes of somecovaient compounds.

• Draw a Lewis representa-tion of the structure ofsome molecules. •

• Compare models andLewis structures ofmolecules.

Materials

wooden or plastic molecular mode! set(ball and stick)

plierselectronegativity tables

Always wear safer/ goggles and a lab apron.

-41-

Pre-Labf

1. Define covaieni bond.

2. Give the electron configuration of oxygen,hydrogen, nitrogen, and carbon.

3. How many covalent bonds will each of oxygen,hydrogen, nitrogen, and carbon form?

4. Describe how electronegativiry differences areused to predict whether a bond is pure covalent,polar covalent, or ionic_t

5. Read the entire laboratory activity. Form ahypothesis about how to show sharing ofelectrons in a covalent bond in an illustrationazid in a model and how the type of bond isdetermined. Record your hypothesis on page 71.

ProcedurePart A

1. Look at your ball-arjd-stick model sets. Identifythe different pieces that represent atoms, singlebonds, double bonds, and triple bonds

2. Select one of every different color of ball- Eachhole that has been bored into the sphere repre-sents a single chemical bond. Count the numberof holes present in the different colored balls.Record your observations in Data)Table 1.

Part B, *>

1. Use an electro negativity table (see page 169 inyour textbook) to determine the electroneg an virydifference between me two elements in the com-pounds in Data Table 2.

2. Use the tables on the right to determine the•percentage of ionic character and bond type ofeach of the compounds. Record your answers on•Data Table 2.

Part C

1 - •'Construct a model for K2.

Z. Compute the eiectronegativity difference for theatoms in the molecule and identify the rype ofboad. Record your answer on Data Table 3.

3. Draw the Lewis structure for the molecule in thesnace provided on Data Table 3,

4. After your teacher Has checked your work, dis-assemble the model

5. Repeat stsps 1-4 for each of the compoundslisted in Data Table 3.

Table 1

Eiectronegativity

difference

• • ' o

Greater than zerobut less than 1.7

Greater than 1.7

.

Bond type

pure covaient

polar covaieni

ionic

Table 2

^ ^ ^ Ui 4™iElectro negativity

difference

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.3 ' •"

2.0

2.2

2.4

2.8

3.0

3.2

- ijfiit i- « ["ii(|i-n**if

Type of bond

; pure covalent

poEar covalent

polar covalent

polar covalent

polar covalent

polar covaient

polar covatent '

polar covalent

polar covalent '

ionic

ionic

ionic

ionic

ionic

ionic

ionic

ionic

ir-.l- «"y sS^SS£"$5<

Percent

ionic character

0

1

4

9

15

22

30

• 39

42

56

S3

70

76

B2

86

SS |

92

-42-

Labor story Manual

I Hypothesis Cleanup and Disposal

1. Be sure all slides and springs have been removed,

from the spheres.

2. Nearly reassemble the model kit.

Data and Observations

Ball color

Red

Orange

Yeilow

Green

Number of holes

Blue

Purple

Black

Identity of element

oxygen

bromine

hydrogen

chlorine

nitrogen

Iodine

carbon

Formufa Electro negativity difference . Percent ionic character

KCI

K-,0

Br?

MgE,

HBr

NaBr

MgS

A!2S3

NaC!

F-,

HCI

CO

Type of bond

Laboratory Manual -43-

Class

Analyze and Conclude

1 Observing and Inferring Boch waoExplain che meaning of cnaromtc. .

and carbon dioxide are triatomic molecules.

2 Meeting and interpreting Data Cc^re the appearance of the Lewis stn^re for

' Va'compound with a ball aad stick model or the compound.

I.' Predicting Predict the shapejand Lewis structure for CBr4.

4, Drawing asiruccu

..^ Conclusion Explain why a formre cannot be used to predict bond type.

ula without electroaegadvicy data or a Lews

mare the ball and stick models yoa- constructed, with your Lewisnumber of bonds? What could be some causes for

s. Do any of them differ n ce

2 Naphthalene CC lQKg). a common mgreaent HImodi baHs: melts ac 3Q.2'C. Sodium chlonGefNaCl). common table salt, melts at SOO./CC.^What GO ±ese meiiins points indicate about ihebonding pacers of each compound?

±=a&

.Name Date Class

Three-Dimensional Modelsof Covalent Molecules

Test reference: Chaf «12-416

Pre-Lab DiscussionA singte covalent bond is formed when two atoms share a pair of elec-trons. Each atom provides one of the electrons of the pair. If the twoatoms1 are alike, the bond is said to be nonpoLar covolent. If the atoms areunlike, one exerts a greater attractive force on the electrons, and the bondis polar cot'ofertl. More than one pair of electrons can be shared. Thisresults i n a double o r triple bond. ~ . . .

A group of atoms held together by covalent bonds is called a molecule.Molecules can be either polar or nonpolar. If bonds are nonpolaxvthemolecule is nonpolar. If bonds are polar, molecules can still be nonpolarif the charge distribution throughout the molecule is symmetrical. Amolecule's symmetry depends on its shape, that is, the positions in spaceof the atoms making up the molecule. Some possible shapes are linear,angular (bent), pyramidal, and tetrahedral.

.^-;. Although we represent molecules on paper as being two-dimensionalfor convenience, they are actually three-dimensional. By building molecu-lar models, chemists come to understand the bonding, shapes, and polarity

. of even the most complex molecules.

PurposeBuild three-dimensional models of some simple covalent molecules. Pre-dict their shapes and polarities from knowledge of bonds and moleculepolarity rules.

Equipmentmolecular rnodel building set

SafetyAll genera] lab safety rules should be folio-wed. Always wear safety gogglesand a lab apron or coat when working in the lab.

Procedure1. Qbtiin. 2. molecular model building set Study the color codeidentifying the different kinds of atoms.

.2. Observe^that the following atoms have one hole (bondingsite): hydrogen, fluorine, chlorine, bromine, and iodine. Theatoms with two holes are oxygen and sulfur. A nitrogen atomhas three holes, and a carbon atom has four holes. - -

-45-

CH3OH

H 0

S. Construct models of the following molecules:

H2 ' HF

H20 Q-Ha 2 2

CH< CH2CI2 O2

C12 • N2

NH3 C02

4, Record your observations below.

Observations and Data

Name

hydrogen

water

methane

chlorine

ammonia

hydrogen fluoride

ethyne

dichloromethane

nitrogen

carbon dioxide

methanol " " "- '=•--

hydrogen peroxide '••

Formula

. H2

H2O

CH4

C12

NH3

HF

CH?CLi

N

oxygen

hydrogen sxil&de

Structuralrepresentation

• H—H

O' - / \ H

H

IH—C—H

- iH

a—a

H—K—HI

H

H — F

H—C=C—H

H

HtH—CL—CI

aN=N

o=c=oH

IH—C—OH

HH

o—o/

•-H -

0—0

5 " S

-46-

ShapeMoleculepolarity -

Nam;

ihree-DiiTJensional Models of Covalent Motecules(continued)

: i

Conclusions and Questions1. Which molecules were nonpolar because all bonds were nonpolar?

2. Which molecules had polar covalent bonds but were nonpolar becauseof symmetry? •"

3. Which rv.'o shapes- appeared '.,0 produce polar molecules?

V-4. Name two types of substances that do not contain molecules with'•' covalent bonds.

-47-