Chapter 9 (part 2): Chemical Bonding I: Lewis Theory

Question 1

Bond energies are always ____ because it always _____ energy to break a bond

Answer 1

Positive

Takes

Question 2

A bond is stronger than another when it requires ____ energy to break it (ie. _____ bond energy)

Answer 2

More

Greater

Question 3

A strong and stable bond will cause a molecule to be relatively ______

Answer 3

Inert

Question 4

What two things do bond energies depend on?

Answer 4

The kind of atoms involved in the bond and the type of bond (single, double, triple)

Question 5

The bond energy for tripe bond is _____ than the bond energy for double bonds which is ____ than the bond energy for single bonds

Answer 5

Greater

Greater

Question 6

Bond energies can be used to estimate _____ change of a reaction

Answer 6

Enthalpy

Question 7

When bonds break the process is ____ so bond energy is _____

Answer 7

Endothermic

Positive

Question 8

When bonds form the process is _____ so bond energy is _____

Answer 8

Exothermic

Negative

Question 9

A reaction is Exothermic when ____ bonds are broken and ____ bonds are formed

Answer 9

Weak

Strong

Question 10

A reaction is endothermic when _____ bonds break and ____ bonds form

Answer 10

Strong

Weak

Question 11

Breaking a chemical bond always _____ energy

Answer 11

Requires

Question 12

Forming a chemical bond always _____ energy

Answer 12

Energy

Question 13

Define bond length

Answer 13

The average length of a bond between two particular atoms in a variety of compounds

Question 14

Bond lengths depend on

Answer 14

The kind of atoms involved in the bond and the type of bond (single, double, triple)

Question 15

Define bond stretching vibration (or stretching vibration)

Answer 15

A molecular motion in which a bond stretched and then contracts

Question 16

For bond vibrations to take place, energy much be ______ to the molecule

Answer 16

Supplied

Question 17

Energy that cause bond vibrations can originate from…..

Answer 17

Molecular collisions or from the absorption of electromagnetic radiation in the infrared region

Question 18

Why is energy that cause bond vibrations specifically cause by the infrared region of the electromagnetic spectrum and not other regions?

Answer 18

Because the infrared frequency range of electromagnetic radiation corresponds to the energies of molecular (E =hv)

Question 19

Define infrared (IR) absorption spectroscopy

Answer 19

The measurement of molecular absorption of infrared frequency radiation to give information about molecular structure

Question 20

Define wavenumber

Answer 20

The reciprocal of wavelength

Question 21

In infrared absorption spectroscopy ______ is determined not the wavelength.

Answer 21

Wavenumber

Question 22

The higher the wave number, the ____ the energy of light that was absorbed

Answer 22

Greater

Question 23

As bond strength increases then the wavenumber value of absorption ______

Answer 23

Increases

Question 24

Define polar covalent bond

Answer 24

A covalent bond between two atoms with significantly different electronegativities, resulting in an uneven distribution of electron density

Question 25

Most covalent bonds between dissimilar atoms are actually _____ _____

Answer 25

Polar covalent

Question 26

Define electronegativity

Answer 26

The ability of an atom to attract electrons to itself in a covalent bond

Question 27

Electronegativity ___ across a row

Answer 27

Increases

Question 28

Electronegativity _____ down a column

Answer 28

Decreases

Question 29

Fluorine is the _____ electronegative atom

Answer 29

Most

Question 30

Francium is the _____ electronegative atom

Answer 30

Least Also Is sometimes called the most electropositive

Question 31

Electronegativity follows what rule of thumb perfectly

Answer 31

Righter tighter lower loser

Question 32

What does the degree of polarity in a chemical bond depend on?

Answer 32

The electronegative difference between the two bonding elements (sometimes abbreviated delta EN)

Question 33

The greater the electronegativity difference, the more ____ the bond

Answer 33

Polar

Question 34

If two elements with identical electronegativities form a covalent bond, they share the electrons equals, and the bond is purely _____ or ____ ____

Answer 34

Covalent | Non polar

Question 35

When the electronegativity difference is small (0-0.4) the bond type is ...?

Answer 35

Covalent

Question 36

When the electronegativity difference is intermediate (0.4-2.0) the bond type is ...?

Answer 36

Polar covalent

Question 37

When the electronegativity difference is large (2.0 and up) the bond type is ...?

Answer 37

Ionic

Question 38

How do you quantify the polarity of a bond?

Answer 38

By the size of its dipole moment

Question 39

Define dipole moment

Answer 39

A measure of the separation of positive and negative charge in a molecule

Question 40

What unit is commonly used for reporting dipole moments?

Answer 40

``` The Debye (D) (1D = 3.34 x 10^-30 C•m) ```

Question 41

Define percent ionic character

Answer 41

The ratio of a bonds actual dipole moment to dipole moment it would have if the electron were transferred completely from one atom to the other, multiplied by 100%

Question 42

In general bonds with greater than ____ ionic character are referred to as ionic bonds

Answer 42

50%

Question 43

Define bond energy

Answer 43

The energy required to break 1 mole of the bond in the gas phase