Honors Chemistry: Chapter 7 - Bonding

Honors Chemistry: Chapter 7 - Bonding

OBJECTIVES

Describe the nature of the chemical bond and its relationship to valence electrons.
Use electronegativities to predict the type of bond that will form between given atoms.
Define ionic bond, covalent bond and molecule.
Differentiate between the properties of ionic and covalent bonds.
Define the ionic radius, and use ionic radius to calculate the internuclear distance between ions in a crystal.
Distinguish between non polar, polar and covalent bond.
Use electronegativities to compare the polarities of bonds.
Describe the coordinate covalent bond.
Define polyatomic ions, and describe their bonding characteristics.
Explain metallic properties using the metallic bond concept.
Use Lewis dot structures to show molecular structures.
Illustrate, using examples, the concept of resonance.
13. Be able to write Lewis dot structures for cases that do not obey the octet rule.
Distinguish between shared and unshared electron pairs.
15. Explain how the shared and unshared pairs of electrons determine molecular structures.
Predict the shapes and bond angles of simple molecules based on the VSEPR theory.
Describe hybrid orbital.
Use hybridization theory to explain the bond angles in compound with multiple bonds.
Use hybridization theory to predict the shapes of molecules.
Differentiate between sigma and pi bonding.
Use the bonding theory to explain unsaturated bonds.

Introduction to Bonding: General Concepts (Chemical Bond)

DIRECTIONS: Write the letter preceding the word or expression that best completes the statement.

In a chemical bond, the link between atoms results from the attraction between electrons and (a) Lewis structures; (b) nuclei; (c) van der Waals forces; (d) isotopes

A covalent bond consists of )a) shared electron; (b) a shared electron pair; (c) two electrovalent electrons; (d) an octet of electrons

If two covalently bonded atoms are identical, the bond is identified as (a) nonpolar covalent; (b) polar covalent; (c) nonionic; (d) coordinate covalent

A covalent bond in which there is unequal attraction for the shared electrons is (a) nonpolar; (b) polar; (c) ionic; (d) dipolar

Atoms with a strong attraction for electrons they share with another atom exhibit (a) zero electronegativity; (b) low electronegativity; (c) high electronegativity; (d) Lewis electronegativity.

Bonds with between 5% and 50% ionic character are considered to be (a) ionic; (b) pure covalent; (c) polar covalent; (d) nonpolar covalent.

A nonpolar covalent bond is likely to exist between (a) a metal and a nonmetal; (b) two ions; (c) two identical atoms; (d) an atom and an ion.

The greater the electronegativity difference between two bonded atoms, the greater the percentage of (a) ionic character; (b) metallic character; (c) covalent character; (d) electron sharing.

In which of these compounds is the bond between the atoms NOT a nonpolar bond? (a) Cl2; (b) H2; (c) HCl; (d) O2.

DIRECTIONS: Complete the following statements, forming accurate sentences.

The electrons involved in the formation of a chemical bond are called ______

A chemical bond resulting from electrostatic attraction between positive and negative ions is called a(n)

______

If the electrons involved in bonding spend most of the time close to one atom rather than the other, the bond is

______

DIRECTIONS: Consult your Periodic Table, specifically examine the graph of % ionic character, and answer the following questions.

The percentage of ionic character and the type of bond for the Li-Cl bond in LiCl (electronegativity for Li = 1.0; electronegativity for Cl = 3.0) is ______

The percentage of ionic character and the type of bond for the Br-Br bond in Br2 (electronegativity for Br = 2.8) is ______

Bonding – General Concepts (Ionic Bond)

DIRECTIONS: Write the letter preceding the word or expression that best completes the statement.

In the formula unit of sodium chloride, NaCl stands for one (a) formula unit; (b) molecule; (c) crystal; (d) atom

The chemical formula for an ionic compound represents the (a) number of atoms in each molecules; (b) the number of ions in each molecule; (c) simplest ratio of the combined ions that gives neutrality; (d) total number of ions in crystal structure.

A formula that shows the types and numbers of atoms combined in a single molecule is called (a) molecular formula; (b) ionic formula; (c) Lewis structure; (d) covalent formula.

In a crystal of an ionic compound, each cation is surrounded by anumber of (a) molecules; (b) positive ions; (c) dipoles; (d) anions.

In a crystal, the valence electrons of adjacent ions (a) repel each other; (b) attract each other; (c) neutralize each other; (d) have no effect on each other.

Compared the neutral atoms involved in its formation, the crystal lattice that results is (a) higher in potential energy; (b) lower in potential energy; (c) equal inpotential energy; (d) unstable.

The lattice energy of a compound A is greater that that of a compound B. What can be deducted from this fact? (a) Compound A is not an ionic compound. (b) It will be more difficult to break the bonds in compound A than in compound B. (c) Compound B is probably a gas. (d) Compound A has larger crystals than compound B.

Which of the following is NOT a property of an ionic compound? (a) vaporizes readily at room temperature; (b) brittle; (c) hard; (d) electrical conductor in molten state.

Compared to ionic compounds, molecular compounds (a) have higher boiling points; (b) are brittle; (c) have lower melting points; (d) are harder.

The forces of attraction between molecules in a molecular compound are (a) stringer that the forces of ionic bonding; (b) weaker that the forces of ionic bonding; (c) approximately equal to the forces of ionic bonding; (d) zero.

At room temperature, most ionic compounds will be (a) solids; (b) liquids; (c) gases; (d) molten.

DIRECTIONS: Complete each of the following statement with the best meaning word or expression.

A(n) ______is a shorthand representation of the composition of a substance using atomic symbols and numerical subscripts.

In the NaCl crystal, the packing of Na+ ions and Cl- ions is such that each ion has clustered around it ______of the oppositely charged ions.

In an ionic compound, the orderly arrangement of ions in a crystal is the state of ______energy.

______energy is the type of energy released when one mole of an ionic crystalline compound is formed from gaseous ions.

Bonding: Ionic Bond

1.Which of the following elements form positive ions when they react?

a. Li in Group 1 b. Ni, a transition elementc. S in Group 16d. C in Group 14

2.Explain, in terms of metallic character, why aluminum form a +3 ion much more readily than boron in the same group.

3.Explain why nitrogen forms a -3 ion, N3- , while bismuth, Bi, in the same group, forms a +3 ion, Bi3+ .

4.Why, in ionic crystal, are "+" ions surrounded by "-" ions rather than ions of the same charge?

5.How do you explain the fact that solid ionic compounds do not conduct an electrical current, yet they become conductors when melted?

6.In general, which is larger:

a. a positive ion or the corresponding atom? ______

b. a negative ion or the corresponding atom?______

c. a metal atom or a nonmetal atom in the same period of the Periodic table? ______

d. a metal ion or a nonmetal ion in the same period? ______

7.Give the electron configuration of:

a. Na1+b. Ca2+c. Al3+d. Cl1-e. O2-

8.What charges would you expect for ions of the following metals?

a. Kb. Scc. Lid. Ale. Sr

9.What charges would you expect for the ion of the following nonmetals?

a. Sb. Fc. Nd. Ie. O

10.Which of the following ions have a noble-gas configurations?

a. Cs1+b. Be2+c. In3+d. Mn2+e. Ca2+

11.Name the following ions:

a. NH41+b. CO32-c. NO31-d. ClO31-

12.Write the formula, include the charge, for the following polyatomic ions:

a. sulfateb. phosphatec, hydrogen carbonated. chromate

13.Give the simplest formula of a compound containing:

a. A+ and X-b. C3+ and X 1-c. B2+ and Y2-d. A1+ and Y2-

14.Using the electronegativity table, arrange the following compounds in order of decreasing ionic character:

LiI, BaO, AlCl3, CsF, RbBr, K2S, CaO, ClF, P2S3, F2, NaI, Mg3N2 .

15.What tests might you perform to determine whether a substance is ionic?

16.Write a balanced equations for the reaction of oxygen with

a. Lib. Znc. Scd. Bi(III)

17.Give all the possible the charges of ions formed by the following transition elements:

Agb. Znc. Cud. Fe

18.A certain ionic compound contains 60.7% O, 17.7% N, 15.2% C, 6.37% H. Find the simplest formula of the compound and identify the ions present.

Bond Classification

Classify the bonds between the following pairs of atoms as principally ionic or covalent.

1. Al -Si4. C - H7. Ca - Cl

2. Ba - O5 . Li - S8. F - S

3. Ca - P6. B - N9. Rb - Br

For each of the atom pair listed below, decide whether an ionic or a covalent bond would form between the elements.

10. hydrogen - fluorine12. cobalt - fluorine14. iron - fluorine

11. astatine - beryllium 13. bromine - cerium15. calcium - fluorine

Using any available information, estimate the percent of ionic character in the following bonds.

16. Pb - S18. Na - Br20. Cu - I

17. Ag - Cl19. C - N21. H - O

Covalent Bond: Drawing Lewis Structures

Draw Lewis structures for the following molecules. The central atom is underlined. NOTE the number of

shared and unshared pairs of electrons.

1.PCl323. ClO31-

2.SO42-24.GeF4

3.PO43-25. HBr

4. CH2Cl226.PF3

5. N2O27.NI3

6. CO228.SiH4

7.HCN29.CH3Cl

8.CO30.Br2

9.H2S31. CHBr3

10.H2Te32. CBr4

11.H2CO333. SO3

12. H2S

13. HBr

14. NO31-

15.PO2F21-

16.CO

17.CO2

18.SCl2

19.N31-

20.ClF3

21. CBr4

22.XeF2

Covalent Compounds: Geometry (1)

Determine the number of shared and unshared electron-pairs around the central atom for the following molecules.

1. H2Te2. PF33. BeF24. CBr4

Determine the molecular geometry using the VSEPR theory.

5. AlCl313. PCl3

6. CBr414. H2O

7. BF315. H - Be - H

8. CO216. OF2

F F

9. HCN17. Xe

F F

10. H2CO18. ClO31-

11. SO319. NO31-

12. SF220. N = N = 0

Predict whether the bond angle of each of the following is greater than, less than, or equal to 109.5 o.

21. F - N - F in NF323. F - Te - F in TeF225. F- As - F in AsF5

22. F - Be - F in BeF224. F - O - F in OF226. O - Xe - O in XeO4

List all the bond angles in the following compounds:

H H

27. CH428. H - C = C - H29. H - C = C - H

Covalent Bond: Polar Bonds

1.Arrange the following elements in order of increasing force of attraction for electrons in the bond.

Sb, F, In, O, N, Se, Cl

2.Which of the following bonds is most polar? In each bond, indicate the atom that carries the partial negative charge.

a. H - Ib. P - Ic. As - Brd. N - S

3.Predict whether the following molecules are polar or nonpolar.

a. SO2b. AsCl3c. H2Sed. SO3

e. H2Sf. CO2g. COi. I2

H H

\ /

j. PH3k. SiCl4l. SCl2m. C = C

/ \

Cl Cl

H H

\ /

n. Cl - C - C – Clo. H2O

/ \

H H

OH H H H Cl

/ | | \ /

q. H - O - S p. H - C - C = Or. C = C

\\ / \

O Cl H

Covalent Bond: Hybridization

1.Mixing of atomic orbitals in an atom (usually the central atom) to generate a set of new atomic orbitals is called ______.

2.The ______orbitals will result in four equal-energy bonds.

3.When two equal-energy orbitals are formed as a result of mixing ______and _____ orbitals you obtain sp hybridization.

4.sp3d2 hybrid orbitals will form only in elements of which periods?

5.The most common hybridization for an atom in group 13 is the _____ hybridization; and in group 14 is the ______hybridization.

6.What is the usual hybridization in group 2? ______

7.Determine the hybridization for the following underlined atoms:

Br Br

\ /

a. Teb. Pc. C

/ \ / | \ / \

H H H H H Br Br

d. Ale. O = C = Of H - C = N

/ \

Cl Cl

H H H H H

\ / \ | /

g. Sh C = CI. S

/ \ / \ / | \

H H H H H H H

Bonding: Review - Vocabulary

In the spaces to the left, write the term that correctly completes each statement.

bond anglecovalent radiusionic bondbond axisdelocalized metallic bond bond length electronegativity molecule covalent bond internuclear distance van der Waals radius

conjugated systemdelocalizationdouble bondfunctional isomers

geometric isomershybrid orbitalsisomersLewis electron dot diagram

pi bondshared pairssigma bondtriple bond

unshared pairspotential energybond energy

______1. The average distance along an imaginary line joining the nuclei of two atoms in a molecule is known as the ______.

______2. Named for a physicist, the ____ is the minimum distance between nuclei for atoms on adjacent molecules.

______3. A ______results when two or more atoms form a covalent bond.

______4. The electrostatic force known as the ____ holds two ions together due to their differing charges.

______5. The imaginary line joining the nuclei of two bonded atoms in a molecule is called the ______.

______6. An atom's relative tendency to attract electrons to itself when bound with a another atom is called its ______.

______7. The )_____ is the average number of degrees between two bond axes extending from the same atom.

______8. Adding the radii of two ions in a compound results in their _____.

______9. When atoms with the same or nearly the same electronegativities share electrons, the resulting shared pair or pairs of electrons constitute a ______.

______10. When electrons in metals are ___, they are free to travel among positive ions.

______11. The sum of one ____ with another is the internuclear distance between two atoms.

______12. Delocalized electrons holding metallic atoms together constitute a ____.

______13. In substances with the same molecular formula but different structures, those structures are called ___.

______14.A(n) ___ is formed when two p orbitals overlap sideways with their axes parallel.

______15. Outer electron pairs bonding two nuclei are called _____.

______16. When three orbitals from a single bonding electron cloud, a(n) ___ occurs.

______17. A simplified means of depicting the electrons in an atom's outer level is shown in a(n) ______.

______18. A(n) ___ is formed by the direct overlap of two orbitals.

______19. A single electron cloud

made of two orbitals is considered a(n) ____.

______20. When carbon s and p orbitals merge, they theoretically, form four equivalent ____.

______21. _____ refers to the existence of two or more substances with the same molecular formula, but different structures.

______22. The two non-bonding outer electron pairs are called ______.

______23. A stabilized molecule containing multiple p overlaps is called a(n) ___.

______24. ___are composed of the same atoms bonded in the same order, but with a different arrangement of atoms around a double bond.

______25. Equal sharing of the pi electrons among all the carbon atoms, without confinement to one atom or bond, is known as ____.

______26. ______is a measure of the strength of a chemical bond.

______27. Generally, a chemical change will tend to occur if it leads to a lower state of ______.

28.What factor is most important in determining the type of bond formed between two atoms?

a. the size of atomsb. the physical state of the elements

c. the charge on the nuclei of the atomsd. the energy changes that accompany bond formation

e. the Lewis structure of the atoms

29.Write the electron dot structure of the nitrogen atom.

30.Write the electron dot structure of the chlorine ion.

31.Which of the following ions has the noble-gas configuration?

a. Fe+2b. Pb+2c. Tl+1d. Sn+2e. Ca+2

32.Write the Lewis structure for Br2.

H H

33.How many lone pairs are present in hydrazine, N2H4? N - N

H H

34.How many electrons are there in a double bond?

35.What is the correct arrangement of atoms in the Lewis structure of phosphorus trichloride, PCl3?

36.What is the correct arrangement of atoms in the Lewis structure of NO2Cl?

37.How many valence electrons are there in the Lewis structure of difluoromethane, CH2F2?

38.How many valence electrons are there in the Lewis structure of the perchlorate ion, ClO4-1?

39.Write the Lewis structure for the sulfite atom, SO3-2.

40.Each of the elements shown except one is capable of achieving an expanded octet. Which one is not?

a. Ib. Sc. Od. Xee. P

41.Which of the following compounds has an atom with an expanded octet?

a. SF5b. H2Oc. PCl3d. HBre. NH3

42.Which element can have more than one oxidation number?

a. Cb. Oc. Sd. Fe. Al

43.Which element often has an incomplete octet in its compounds?

a. Fb. Oc. Bd. Xee. P

44.Which of the following is an odd-electron molecule?

a. N2Ob. N2O4c. NH3d. NO3e. N2O5

45.All but one of the following species exhibit the phenomenon of resonance. Which one does not?

a. NO3-1b. SO2c. CO2d. SO4-2e. C6H6

46.All but one of the statements regarding resonance is correct. Which one is incorrect?

a. A species that undergoes resonance changes rapidly from one form to another.

b. Resonance lowers the energy of the species.

c. One Lewis structure will not properly describe a molecule that undergoes resonance.

d. Resonance involves changing the positions of double bonds in Lewis structures.

e. Resonance averages out certain bond lengths in a Lewis structure.

47.Which of the following structures represent resonance structures of a single species?

:X=A-X: X-A=X: :X-X=A:

I II III

a. I and IIIb. I and IIc. II and IIId. I, II, and IIIe. none of the above

48.Which molecule has a central atom with an expanded octet?

a. CO2b. XeF4c. CF4d. SO3e. NCl3

49.Which molecule has a central atom with an incomplete octet?

a. CH4b. BeF2c. N2d. SO2e. PBr3

For the questions 50 through 55 answer the following:

1.How many electron pairs surround the central atom ?

2. What is the shape of the molecule?

# of electron pairsShape

50. CBr4______

51.SF4______

52.CO3-2______

53.SO2______

54.GaCL3______

55. TeCl4 ______

56.What is the effect of lone pairs of electrons on bond angles?

57.Which bond is predominantly ionic?

a. Ge-Fb. Sn-Clc. As-Brd. N-Oe. So-O

58.Which of the following is polar?

a. CO2b. NH3c. CF4d. BF3e. SeO2

59.A molecule consists of a central atom surrounded by some number of atoms of the same element. What shape molecule of this type is likely to be polar?

a. linearb. octahedralc. square planard. T-shapede. trigonal planar

60.Which of the following is nonpolar?

a. SeO2b. CH3Fc. H2Od. ClF3e. XeF4

61.One of the following does not apply to a covalent bond. Which one?

a. electron pairsb. electrons are sharedc. orbitals overlapd. may be polar

e. electrons localized on one atom

62.What hybridization is associated with a trigonal planar arrangement of electron pairs?

a. sp3db. sp2c. sp3d2d. spe. sp3

63.What hybridization is associated with an octahedral arrangement of electron pairs?

a. sp3db. sp2c. sp3d2d. spe. sp3

64.What arrangement of electron pairs occurs with sp3 hybridization?

a. trigonal planarb. T-shapedc. octahedral

d. tetrahedrale. trigonal bipyramidal

65.An octahedral arrangement of electron pairs can lead to all of the molecular shapes given except one. Which molecular shape cannot arise from an octahedral arrangement of electron pairs?

a. trigonal planarb. octahedralc. square planar

d. square pyramidale. linear

66.An AB4 molecule has two lone pairs. What is the hybridization of the central atom?

a. sp3db. sp2c. sp3d2d. spe. sp3

67.Head-to-head overlap of an sp3 hybrid orbital with an sp2 hybrid orbital creates a

a. double bondb. sigma bondc. pi bondd. triple bond

68.A triple bond consists of

a. three sigma bondsb. one sigma bond and two pi bonds

c. two sigma bonds and one pi bondd. three pi bondse.

69.Side-by-side overlap of a p-orbital with another p-orbital creates a

a. single bondb. sigma bondc. pi bondd. triple bond

70.An atom with the valence electron configuration shown is expected to form four sigma bonds. What hybridization is expected?

   

s p p p

a. spb. sp3c. sp3dd. sp2e. sp2d3

SELF-TEST: CHAPTER 7

1.The total number of electron pairs around phosphorus for PCl5 is: a. 2 b. 3 c. 4d. 5e. 6

2.An atom X is surrounded by 3 sigma bonds and 1 pi bond. The bond angle around the central atom is

a. 90ºb. 109ºc. 120ºd. 180º

3.An atom X is surrounded by an unshared pair of electrons, 2 sigma bonds and one pi bond. The hybridization for the molecule with X as central atom is a. sp b. sp2 c. sp3 d. sp3d e. sp3d2

4.Which of the following bonds would be most polar?a. C-C b. C-O c. C-F d. C-N

5.All of the following molecules have double bonds except: a. BeF2 b. CO2 c. SO3 d. NO

6.Arsenic pentafluoride forms an expanded octet. Which of the following statements are true?

a. There are five bonds to the central atom.