Chapter 8 - Review Questions

The formal charge on the nitrogen atom in the nitrate ion (NO31-) is _____.

+1

If an atom has the electron configuration 1s22s22p3, how many electrons must it gain to achieve an octet?

3 electrons

How many hydrogen atoms must bond to silicon to give it an octet of valence electrons?

4

There are ________ paired and ________ unpaired electrons in the Lewis symbol for a fluorine atom.

6, 1

The halogens, alkali metals, and alkaline earth metals have ________ valence electrons, respectively.

7, 1, and 2

Lattice energy is ________.

the energy required to convert a mole of ionic solid into its constituent ions in the gas phase

How many electrons should be shown in the Lewis symbol for hydrogen?

1

A double bond consists of ________ pairs of electrons shared between two atoms.

2

There are ________ unpaired electrons in the Lewis symbol for an oxygen atom .

2

How many electrons must a sulfur atom gain to achieve an octet in its valance shell?

2 electrons

There are ________ valence electrons in the Lewis structure of CH3OCl.

20

A triple bond consists of ________ pairs of electrons shared between two atoms.

3

How many equivalent resonance structures can be drawn for the molecule of SO3 without having to violate the octet rule on the sulfur atom?

3

Based on the octet rule, aluminum most likely forms an ________ ion.

Al3+

In the molecule HCl, which atom is the negative pole?

Cl

__________ difference can be used to predict bond type. If electronegativities differ by __________, the bond is substantially ionic; if they differ by __________, the bond is polar covalent; and if the values are __________, the bond is nonpolar covalent.

Electronegativity more than 2 units less than 2 units equal

Given the bond B−F, the more electronegative atom in the bond is _____. Given the bond H−I, the more electronegative atom in the bond is _____. Given the bond P−N, the more electronegative atom in the bond is _____.

F I N

T/F: Atoms surrounded by eight valence electrons tend to lose electrons.

False

T/F: If a molecule has polar bonds, the molecule is polar.

False

T/F: When a metal loses an electron, the process is exothermic.

False

T/F: If you break a chemical bond, energy is released.

False; Breaking a chemical bond requires an input of energy/ If you break a chemical bond, energy is absorbed

T/F: C-C bonds are stronger than C-H bonds.

False; C-H is stronger (Table 8.3)

T/F: The longer the bond, the larger the bond enthalpy.

False; For the same atom pair, the longer the bond the smaller the bond enthalpy.

T/F: The hydrogen atom is the most stable when it has a full octet of electrons.

False; Hydrogen can only have 2 electrons at most

T/F: A typical single bond length is in the 5-10A range.

False; The single bond lengths (in Table 8.4) are all less than 5A

Which element never follows the octet rule?

H

Based on the octet rule, iodine most likely forms an ________ ion.

I-

Based on the octet rule, magnesium most likely forms a ________ ion.

Mg2+

Which of the following would have to gain two electrons in order to achieve a noble gas electron configuration? O Sr Na Se Br

O, Se

Of the molecules SiF4 and SiBr4, which has bonds that are more polar?

SiF4

Which of the following would have to lose two electrons in order to achieve a noble gas electron configuration? O Sr Na Se Br

Sr

T/F: Energy is stored in chemical bonds.

True

The electron configuration of the S2- ion is ________.

[Ne]3s23p6

The electron configuration of the sulfide ion (S2-) is ________.

[Ne]3s23p6

Ionic bonding occurs between __________ (__________).

a cation and an anion (often a metal and a nonmetal)

Which choice below correctly lists the elements in order of increasing electronegativity (least --> most)? a) C < N < O < F b) N < C < O < F c) N < C < F < O d) C < N < F < O

a) C < N < O < F

In which of the molecules below is the carbon-carbon distance the shortest? a) H-C≡C-H b) H2C=C=CH2 c) H3C-CH2-CH3 d) H3C-CH3 e) H2C=CH2

a) H-C≡C-H

Select the most electronegative atom in each of the following sets: a) Na, Mg, K, Ca b) P, S, As, Se c) Be, B, C, Si d) Zn, Ge, Ga, As

a) Mg b) S c) C d) As

Which molecule below has an unpaired electron? a) NO2 b) NH3 c) BF3 d) PF5

a) NO2

Which molecule below violates the octet rule? a) PF5 b) CH4 c) NBr3 d) OF2

a) PF5

For atoms X and Y, the bond length of an X—Y bond is _______ the bond length of an X=Y bond. a) greater than b) less than c) equal to d) variable to (depending on X and Y)

a) greater than

Which of the following bonds are polar? a) B−F b) Cl−Cl c) P−N d) H−I

a)B−F, c) P−N, d) H−I

Which of these molecules has a Lewis structure with a central atom having no nonbonding electron pairs? a) CO2 b) PF3 c) SiF4 d) H2S

a)CO2, c)SiF4

Bond enthalpy is ________.

always positive

The ________ ion has a noble gas electron configuration. a) Li- b) Be2+ c) Be d) Li2+ e) B2+

b) Be2+

Which of the following does not have eight valence electrons? a) Xe b) Ca+ c) Br- d) Rb+ e) All of the above have eight valence electrons.

b) Ca+

The Lewis structure of HCN (H bonded to C) shows that ________ has ________ nonbonding electron pair(s). a) C, 2 b) N, 1 c) H, 1 d) C, 1 e) N, 2

b) N, 1

Which of the following compounds has the highest boiling point? a) F2 b) NaF c) HF d) ClF

b) NaF

For atoms X and Y, the bond enthalpy of an X—Y bond is _______ the bond enthalpy of an X=Y bond. a) greater than b) less than c) equal to d) variable to (depending on X and Y)

b) less than

The carbon disulfide (CS2) molecule has __________. a) two single bonds b) two double bonds c) a single bond and a double bond d) a single bond and a triple bond

b) two double bonds.

Which of these elements is most likely to form ions with a 2+ charge? a) Li b) P c) Ca d) O e) Cl

c) Ca

Which compound below has the largest lattice energy? a) NaCl b) KBr c) CaO d) CsI

c) CaO

The ________ ion has a noble gas electron configuration. a) Cl b) F+ c) P3- d) F2+ e) N4-

c) P3-

Which statement correctly describes triple bonds? a) Three electrons are shared. b) The octet rule is violated. c) Three pairs of electrons are shared. d) They are often formed by oxygen.

c) Three pairs of electrons are shared.

The ability of an atom in a molecule to attract electrons is best quantified by the ________. a) electron charge-to-mass ratio b) first ionization potential c) electronegativity d) diamagnetism e) paramagnetism

c) electronegativity

Boron trifluoride (BF3) is used as a catalyst in many organic synthesis reactions. What type of bonding occurs between the atoms of a BF3 molecule?

covalent

In a __________ between two atoms, the more electronegative atom will _____ more electron density toward itself, causing a polar bond. The more electronegative element is the _____ pole, whereas the less electronegative element is the _____ pole. The direction of the dipole is always ______ the more electronegative element.

covalent bond attract negative positive toward

Which of the following statements about electronegativity is false? a) Fluorine is the most electronegative element. b) Cesium is the least electronegative element. c) The numerical values for electronegativity have no units. d) Electronegativity is the same thing as electron affinity. e) Electronegativity is the ability of an atom in a molecule to attract electron density toward itself.

d) Electronegativity is the same thing as electron affinity.

Of the molecules below, the bond in ________ is the most polar. a) HI b) H2 c) HCl d) HF e) HBr

d) HF

Which of the following bonds is the most polar? a) Se−F b) N−P c) H−I d) H−F e) Ga−Cl

d) H−F

The most electronegative atom of the ones listed below is ________. a) Te b) Sn c) Sb d) I e) In

d) I

Of the atoms below, ________ is the most electronegative. a) N b) P c) Se d) O e) S

d) O

Which one of these statements about formal charge is true? a) Formal charge is used in calculating the dipole moment of a diatomic molecule. b) Formal charge takes into account the different electronegativities of the atoms in a molecule. c) Formal charge is most useful for ionic compounds. d) To draw the best Lewis structure, you should minimize formal charge. e) Formal charge is the same as oxidation number.

d) To draw the best Lewis structure, you should minimize formal charge.

What species has the electron configuration [Ar]3d2? a) Mn2+ b) Fe3+ c) Cr2+ d) V3+ e) K+

d) V3+

The hydrogen cyanide (HCN) molecule has __________. a) two single bonds b) two double bonds c) a single bond and a double bond d) a single bond and a triple bond

d) a single bond and a triple bond

Both of the sulfur-oxygen double bonds in SO2 are polar. In which direction should the polarity arrows point? a) to the right b) to the left c) toward the central sulfur atom d) away from the central sulfur atom

d) away from the central sulfur atom

The Lewis structure of N2H2 shows ________. a) each hydrogen has one nonbonding electron pair b) a nitrogen-nitrogen single bond c) a nitrogen-nitrogen triple bond d) each nitrogen has one nonbonding electron pair e) each nitrogen has two nonbonding electron pairs

d) each nitrogen has one nonbonding electron pair

Does the lattice energy of an ionic solid increase or decrease as the sizes of the ions increase?

decrease

How do electronegativity values generally vary going down a column in the periodic table?

decrease

The ________ ion has eight valence electrons. a) Co7+ b) Ni7+ c) Sc7+ d) Cu7+ e) Mn7+

e) Mn7+

Which of the following has eight valence electrons? a) Cl- b) Kr c) Na+ d) Ti4+ e) all of the above

e) all of the above

The octet rule states that atoms tend to gain, lose, or share electrons until they have _______ valence electrons.

eight

A nonpolar bond will form between two ________ atoms of ________ electronegativity.

identical, equal

Does the lattice energy of an ionic solid increase or decrease as the charges of the ions increase?

increase

What is the trend in electronegativity going from left to right in a row of the periodic table?

increase

The two types of chemical bonds commonly found in compounds are __________.

ionic and covalent

Metals have _____ electronegativity compared to nonmetals.

low

Metallic bonding occurs between __________.

metals

Covalent bonding occurs between __________.

nonmetals

When two bonded atoms attract electrons with equal strength, the result is a __________. A __________ is one in which the electrons are unequally shared between the atoms. An __________ results when the sharing is so unequal that fully charged ions form.

nonpolar covalent bond polar covalent bond ionic bond

Resonance structures differ by ________.

placement of electrons only

Which of the following bonds are polar? Which is the more electronegative atom in each polar bond? a) B-F b) Cl-Cl c) Se-O d) H-I

polar, F nonpolar polar, O polar, I

Covalent bonds involve the __________ of valence electrons. Valence electrons are those in the __________ of an atom

sharing; outermost subshell

The Lewis symbol for a sulfur atom includes how many dots?

six

Lewis symbols and Lewis structures (electron-dot structures) are used to show __________.

valence electrons and covalent bonding