Smartbook Chapter 6 (6.1-6.6)

Which of the following are common instances in which an exception to the octet rule can exist for a Lewis structure?

- A central atom from either Group 2 or 3 has less than a full octet of electrons. - A central atom from Period 3 or beyond has more than a full octet of electrons. - A single atom possesses an odd number of electrons.

How does drawing the Lewis structure of a polyatomic ion differ from drawing the Lewis structure of a neutral molecule?

- Brackets are placed around the Lewis structure and the charge is indicated. - The number of valence electrons must be adjusted to account for the charge.

Which statements about the magnitude of dispersion forces are correct?

- Dispersion forces are greater in heavier molecules. - Dispersion forces tend to increase with increasing size.

Which of the following are steps in drawing a valid Lewis structure?

- Draw a skeletal structure of the molecule. - Ensure that every atom has a full octet of electrons, except for hydrogen. - Count the number of valence electrons using the formula.

Which of the following are steps in determining the molecular shape of a compound?

- Draw a valid Lewis structure. - Count the electron groups around the central atom.

Which properties of a substance are influenced by the strength of its intermolecular forces?

- Melting point - Boiling point

In which instances might actual bond angles deviate from ideal bond angles?

- Not all of the electron groups are bonding groups. - Not all of the surrounding atoms are the same.

Trends in electronegativity on the period table

- Within a period, electronegativity increases from left to right. - Within a group, electronegativity decreases from top to bottom.

In a substance exhibiting dipole-dipole forces, the partially ______ end of one molecule will align itself with the partially ______ end of another.

- positive; negative - negative; positive

Order the steps used to determine the molecular shape of a given compound, beginning with the first step at the top.

1) Draw a valid Lewis Structure 2) Count the number of electron groups around the central atom 3) Apply VESEPR theory to determine the electron group geometry 4) Consider the positions of the atoms (excluding lone pairs) in the module.

Place the steps for determining the polarity of PCl3 in the correct order.

1) The lewis structure has four electron groups around the central atom 2) The electron group geometry is tetrahedral 3) The presence of one nonbonding pair makes the molecular shape trigonal pyramidal 4) The Molecule is polar

Tetrahedral

109.5 degrees

Linear

180 degrees

The most common Lewis structures for molecules with beryllium (Be) or boron (B) as the central atom have ____ electrons around Be and ____ electrons around B, respectively.

4,6

In general, the larger the molecule, matches = the stronger the dispersion forces. In general, the smaller the molecule, matches = the weaker the dispersion forces. Dispersion forces tend to increase matches = with increasing molar mass. Dispersion forces tend to decrease matches = with decreasing molar mass.

All True

Which lettered region of the periodic table (shown) contains the elements with the smallest electronegativity values?

B

A line drawn between two atoms in a molecule

Bonding pair of electrons

Rank the following nonpolar species in order of increasing dispersion forces with the smallest at the bottom.

C20H42 C8H18 C5H12 C3H8 CH4

Which of the following pairs is arranged with the species having stronger dispersion forces listed last?

CH4, CF4

In which instance below would the bond angles be likely to deviate from the ideal? Assume the central atom does not have an expanded octet.

Central atom is bonded to three identical atoms and has a nonbonding pair.

Polar covalent bond with the electronegativity difference between the atoms comprising it

Difference between 0.5 and 2.0

Ionic bond with the electronegativity difference between the atoms comprising it

Difference greater than or equal to 2.0

Nonpolar covalent bond with the electronegativity difference between the atoms comprising it

Difference less than 0.5

Select all of the intermolecular forces that exist between molecules of CHBr3 (carbon is the central atom).

Dipole-dipole forces Dispersion forces

Intermolecular Force > Nonpolar molecule < it experiences

Dispersion forces

Select all of the intermolecular forces that exist between molecules of CH3CH2NH2.

Dispersion forces Dipole-dipole forces Hydrogen bonding

Intermolecular Force > Polar molecule < it experiences

Dispersion forces and dipole-dipole forces

Intermolecular Force > Molecule containing F-H, O-H, or N-H bonds < it experiences

Dispersion forces, dipole-dipole forces, hydrogen bonding

___ is a measure of the tendency of an atom of a given element to attract shared electrons to itself in a covalent bond.

Electronegativity

T or F Any compound that contains both hydrogen and nitrogen atoms is capable of hydrogen bonding, assuming the atom bonded to H has one or more lone pairs.

False

T or F An arrow used to indicate a partial separation of charge in a bond or molecule is called a dipole. True false question.

False

The various electrostatic attractions that hold particles of a given substance together are collectively known as _____ forces.

Intermolecular

What are dipole-dipole forces?

Intermolecular forces between polar molecules

Use differences in electronegativity to classify each of the bonds below. Instructions K and Cl

Ionic

strength of intermolecular forces with its expected effect on the physical properties of substances. Weaker the intermolecular forces relative to thermal energy

Lower boiling point

When the chemical formula of a molecular compound contains more than one unique atom, the atom with the greatest character ____ is placed as the central atom in the Lewis structure.

Metallic

How does molecular geometry differ from electron-group geometry?

Molecular geometry considers only the placement of atoms in a molecule, not the nonbonding electrons.

Which structural features would cause a compound to experience hydrogen bonding as an intermolecular force? Assume the atom bonded to H has one or more lone pairs.

N--H bond F--H bond O--H bond

Two dots surrounding an atom in a molecule

Nonbonding pair of electrons

Use differences in electronegativity to classify each of the bonds below. Instructions B and H

Nonpolar Covalent

Use differences in electronegativity to classify each of the bonds below. Instructions C and O

Polar Covalent

Which type of molecules exhibit dipole-dipole intermolecular forces?

Polar molecules

In VSEPR theory, an electron group can be _____, ____, ____ and ____.

Single bond, double bond, triple bond and nonbonding pair

Rule for drawing N2H4 Lewis structure.

The molecule contains more than one central atom.

Rule for drawing CH3Br Lewis structure.

The unique atom with the greatest metallic character is the central atom.

No single resonance structure adequately describes the structure of a molecule.

True

Resonance structures differ only in the placement of their electrons.

True

T or F A diatomic molecule that contains a polar bond will be polar.

True

T or F A diatomic molecule whose bond is nonpolar will be nonpolar.

True

When two or more valid resonance forms of a molecule are possible, the actual structure of the molecule is a single combination of the various resonance forms.

True

What are resonance structures?

Two or more valid Lewis structures of a compound that differ in the placement of their electrons

The electron groups in the valence shell of an atom will repel each other. This is the basis for ______.

VESPR Theory

Are these statements about intermolecular forces are correct -They exist between particles of any substance. -They are electrostatic in nature.

Yes

Do the following statements correctly describe how to indicate the shift of electron density in a polar bond? - A dipole arrow is placed above the bond under consideration. - The head of the arrow is placed above the more electronegative atom.

Yes

What is electronegativity?

ability of an atom to attract electronsThe tendency of an atom to attract shared electrons to itself in a covalent bond

Electron geometry around a central atom considers ______, while molecular geometry considers ______.

all electron groups; bonded atoms only

In describing the molecular geometry of a given compound, only the _____ are considered, not the nonbonding electrons.

atoms

Whether a polyatomic molecule is polar depends on both ______ and ______.

bond polarity; molecular shape

Strong electrostatic attractions between molecules having highly polarized bonds to hydrogen are known as hydrogen ___.

bonding

The three types of intermolecular forces that exist between electrically neutral molecules are ______.

dispersion forces, hydrogen bonding, and dipole-dipole forces

In VSEPR theory, nonbonding pairs, as well as single, double, and triple bonds, are all examples of ______.

electron groups

Some elements do not obey the octet rule because they have more than eight valence electrons, that is, they have a(n) ___ valence shell. This is only possible for elements from Period ___ of the periodic table onward.

expanded, 3

strength of intermolecular forces with its expected effect on the physical properties of substances. Stronger intermolecular forces

higher boiling point

The particularly strong intermolecular forces between molecules containing H-F, H-O, or H-N bonds are called ______.

hydrogen bonds

In general, dispersion forces ______ with increasing molecular size and ______ with decreasing molecular mass.

increase; decrease

The strength of dispersion forces ______ with increasing size and molar mass. This will cause a large hydrocarbon such as decane, C10H22, to have a ______ melting point than propane, C3H8.

increases; higher

A pair of electrons drawn as dots surrounding an atom in a Lewis structure is known as a ______ pair.

nonbonding

The image shown is the Lewis structure of CCl4 showing the dipole vectors of the individual bonds. Any time there are identical bonds symmetrically distributed around a central atom, with no lone pairs, the molecule be _____ because the bond dipoles will vectorially add up to _____.

nonpolar; zero

A Lewis structure will usually require one or more multiple bonds if there is an atom present that does not have a full ____ after all available electrons have already been placed. The multiple bond is formed by exchanging one ____ electron pair for each new bond.

octet, non-bonding

One or more multiple bonds are used in a Lewis structure when ______.

one or more atoms lack a complete octet after all electrons have been allotted

A bond in which electrons are shared unequally between atoms is a ____ covalent bond.

polar

Regardless of the terminal atoms, a trigonal pyramidal molecule will be _____ because the bond dipoles are _____ distributed.

polar; unsymmetrically

Because F, O, and N (mnemonic: "let's have FON") are so electronegative, a bond between one of them with hydrogen is highly polar. Their small atomic sizes result in very concentrated charges. This results in "hydrogen bonding" where the large partial _____ charge on H is very strongly attracted to lone pair and large partial _____ charge of F, O, or N on a neighboring molecule.

positive; negative

VSEPR theory is based on the fact that the electron groups in the valence shell of a central atom will ___ each other.

repel

Two or more valid Lewis structures that differ only in the placement of their electrons are known as ___ structures.

resonance

A polar covalent bond is one in which electrons are ______ unequally between atoms.

shared

N-H, O-H, or F-H bonds are necessary for hydrogen bonding because the ______ sizes and ______ electronegativities of N, O, and F make their bonds to hydrogen highly polar.

small; high

A bond angle is ______.

the angle between the bonding electron groups of a central atom