Chapter 3: Bonding and Chemical Interactions

Question 1

Which element?

____________ can only have 2 valence electrons.

Answer 1

Hydrogen

Question 2

Which elements?

________ and ____________ bond to attain 2 and 4 valence electrons, respectively.

Answer 2

Lithium and beryllium

Question 3

Which element?

________ bonds to attain 6 valence electrons.

Answer 3

Boron

Question 4

All elements in period ____ and greater can expand the valence shell to include more than 8 electrons by incorporating the ____-orbitals.

Answer 4

3; d

Question 5

An ________________ octet can occur in elements that are stable with fewer than 8 electrons in their valence shell, and include hydrogen (2), helium (2), lithium (2), beryllium (4), and boron (6).

Answer 5

incomplete

Question 6

An ________________ octet can occur in any element in period 3 and greater; they can hold more than 8 electrons. This includes phosphorus (10), sulfur (12), chlorine (14), and many others.

Answer 6

expanded

Question 7

Any molecules with an odd number of valence electrons (can/cannot?) distribute those electrons to give 8 to each atom - cannot achieve the octet rule.

Answer 7

cannot

Question 8

Which 6 elements almost always abide the octet rule?

Answer 8

1. carbon
2. nitrogen
3. oxygen
4. fluorine
5. sodium
6. magnesium

Question 9

In ________ bonding, 1+ electrons from a low IE element are transferred to an atom with high electron affinity.

typically metal to nonmetal

Answer 9

ionic

Question 10

What holds ionic bonds together? This type of attraction creates ________ structures consisting of repeating rows of cations and anions, rather than individual molecular bonds.

Answer 10

The electrostatic attraction between opposite charges; lattice

Question 11

In ____________ bonding, an electron pair is shared between 2 atoms, typically nonmetals, that have similar values of electronegativity.

Answer 11

covalent

Question 12

The degree to which the pair of e- is shared (un)equally between 2 atoms determines the degree of ____________.

Answer 12

polarity

Question 13

If the e- pair is shared equally, the bond is ____________. If unequally, the bond is ________. If both of the shared electrons are contributed by only one of the 2 atoms, the bond is called ________________ ____________.

Answer 13

nonpolar; polar; coordinate covalent

Question 14

Unlike ionic crystal lattices, covalent compounds consist of what?

Answer 14

Individually bonded molecules

Question 15

________ bonds form between atoms that have significantly different electronegativies.

Answer 15

ionic

Question 16

Atoms that lose electrons are ________, atoms that gain electrons are ________.

Answer 16

cations; anions

Question 17

Electrons are not ________ in an ionic bond, but rather ________________.

Answer 17

shared; transferred

Question 18

What value?

For electron transfer to occur, the difference in electronegativity should be greater than ____ on the Pauling scale.

Answer 18

1.7

Question 19

Because of the strength of electrostatic forces between constituents of ionic compounds, they have (low/high?) melting and boiling points.

Answer 19

very high

Question 20

Ionic compounds also ________ in water and other polar solvents, and are good ____________ of electricity in the molten or aqueous state.

Answer 20

dissolve; conductors

Question 21

In an ionic lattice structure, the attractive forces between oppositely charged ions are ____________ and repulsive forces between ions of like charge are ____________.

Answer 21

maximized, minimized

Question 22

When 2+ atoms with similar ________________ interact, energy required to form ions through the complete transfer of 1+ electrons is greater than the energy that would be released upon formation of an ionic bond.

Answer 22

electronegativities

instead, they share electrons

i.e. 2 atoms of similar tendency would not form an ionic compound because it is energetically unfavorabel

Question 23

Covalent compounds contain discrete molecular units with relatively (weak/strong?) intermolecular forces.

Answer 23

weak

Question 24

The number of shared electron pairs between 2 atoms is called the ________ ________.

Answer 24

bond order

single bond = order of 1
double bond = 2
triple bond = 3

Question 25

________ ________ is the average distance between 2 nuclei of atoms in a bond.

Answer 25

bond length

Question 26

As the # of shared e- pairs increases, what happens to bond length?

Answer 26

The 2 atoms are pulled closer together and bond length decreases

Question 27

________ ________ is the energy required to break a bond by separating its components into their isolated, gaseous atomic states.

Answer 27

bond energy

Question 28

The greater the # of pairs of e- shared between atomic nuclei, the (less/more?) energy is required to break these bonds.

Answer 28

more

Question 29

The greater the bond energy, the (weaker/stronger?) the bond.

Answer 29

stronger

Question 30

____________ occurs when 2 atoms have a relative difference in electronegativities. The atom with higher EN gets the larger share of e- density.

Answer 30

polarity

Question 31

A polar bond creates a ________, with the positive end at the less EN atom and the negative end at the more EN atom. | partial charges!!

Answer 31

dipole

Question 32

When atoms have (nearly) identical EN, they get an equal distribution of e-. This is a ____________ ____________ bond.

Answer 32

nonpolar covalent | no separtion of charge

Question 33

What are the 7 common diatomic molecules?

Answer 33

1. H_{2 2. N2 3. O2 4. F2 5. Cl2 6. Br2 7. I2}

Question 34

# What value? Any bond between atoms with a difference in EN less than ____ is generally considered nonpolar.

Answer 34

0.5

Question 35

Atoms that differ moderately in their electronegativities will share e- unevenly, creating ________ ________________ bonds.

Answer 35

polar covalent

Question 36

The difference in EN should be between ____ and ____.

Answer 36

0.5 and 1.7

Question 37

Polar covalent bonds don't form ionic bonds, but due cause a ________________ of charge across the bond.

Answer 37

separation

Question 38

The ____________ ____________ of the polar bond or polar molecule is a vector quantity.

Answer 38

dipole moment

Question 39

The vector quantity of a polar bond is given by what equation? What does each qty stand for?

Answer 39

p = qd | p = dipole moment q = magnitude of charge d = displacement ## Footnote Equation 3.1

Question 40

The dipole moment vector, represented by an arrow pointing from the positive to negative charge, is measured in ____________ ________. What is it?

Answer 40

Debye units - coulomb meters

Question 41

In a ________________ ____________ bond, both shared electrons originated on the same atom. This means that a lone pair of one atom attacked another atom with an unhybridized p-orbital to form a bond.

Answer 41

coordinate covalent

Question 42

Coordinate covalent bonds are typically found in ________ ____-____ reactions.

Answer 42

Lewis acid-base

Question 43

A Lewis acid is any compound that ________________.

Answer 43

accepts a lone pair of e-

Question 44

A Lewis base is any compound that ________________.

Answer 44

donates a pair of e-

Question 45

The electrons involved in a covalent bond in the valence shell are ____________ electrons. Those not involve are ________________ electrons.

Answer 45

bonding; nonbonding

Question 46

The unshared e- pairs are known as ________ pairs, because they are associated with only one atomic nucleus.

Answer 46

lone

Question 47

Formal charge is what? How is it calculated?

Answer 47

The charge assigned to an atom or molecule It is calculated by the number of valence electrons minus the number of **nonbonding** valence electrons minus 1/2 the total number of electrons shared in bonds ## Footnote Formal charge = valence electrons - dots - sticks

Question 48

________ structures represent how the electrons are arranged around individual atoms in a molecule.

Answer 48

Lewis

Question 49

The arrangement that ________________ the # and magnitude of formal charges is usually the most stable arrangement of the compound.

Answer 49

minimizes

Question 50

Each dot on a Lewis dot diagram represents what?

Answer 50

an s or p valence electron of an atom

Question 51

For Lewis structures, the least ____________________ atom is the central atom.

Answer 51

electronegative

Question 52

Formal charge ____________ the effect of EN difference, and oxidation numbers ____________ the effect of EN difference.

Answer 52

underestimate; overestimate ## Footnote in oxidation state, we assume the more EN atom has 100% of the bonding e- share

Question 53

It may be possible to draw 2+ Lewis structures that demonstrate the same arrangement of atoms but that differ in the specific placement of electrons. These are ____________ ____________, and are represented with a double-headed arrow.

Answer 53

resonance structures

Question 54

The more stable a resonance structure is, the more it contributes to the ________________ of the resonance hybrid.

Answer 54

character

Question 55

A Lewis structure with ________ or ____ formal charges is preferred over one with large formal charges.

Answer 55

small/ no

Question 56

A Lewis structure with ____ separation between opposite charges is preferred

Answer 56

less

Question 57

A Lewis structure where negative formal charges are placed on ____ EN atoms is more stable.

Answer 57

more

Question 58

____________ geometry describes the spatial arrangement of all pairs of electrons around the central atom, including both bonding and lone pairs.

Answer 58

Electronic | most important for **ideal bond angle**

Question 59

____________ geometry describes the spatial arrangement of *only* the bonding pairs of electrons.

Answer 59

Molecular | main focus of MCAT

Question 60

The ________________ number, which is the # of atoms that surround and are bonded to a central atom, is the relevant factor when determining molecular geometry.

Answer 60

coordination

Question 61

Nonbonding pairs are exert (more/less?) repulsion than bonding pairs because these electrons reside closer to the nucleus.

Answer 61

more

Question 62

A compound with nonpolar bonds is always ________.

Answer 62

nonpolar

Question 63

If the compound has a molecular geometry such that the bond dipole moments cancel each other out, then the result is a ____________ compound.

Answer 63

nonpolar | usually symmetrical

Question 64

When 2 atoms bond to form a compound, the atomic orbitals interact to form a ________________ orbital that describes the probability of finding the bonding electrons in a given space.

Answer 64

molecular

Question 65

Molecular orbitals are obtained by combining the ________ ____________ of the atomic orbitals.

Answer 65

wave functions

Question 66

If the signs of the 2 atomic orbitals are the **same**, a ____________ orbital forms. If **different**, an ________________ orbital forms.

Answer 66

bonding; antibonding

Question 67

When orbitals overlap head-to-head, the resulting bond is a ________ bond. These allow for free rotation because the e- density of the bonding orbital is a single linear accumulation between atomic nuclei.

Answer 67

sigma

Question 68

When orbitals overlap to form 2 parallel e- cloud densities, a ____ bond is formed. They do not allow for free rotation because the e- densities are parallel and cannot be twisted.

Answer 68

pi

Question 69

Atoms and compounds can participate in weak electrostatic interactions. What are the 3 types of intermolecular forces (IMFs)?

Answer 69

1. London dispersion forces 2. dipole-dipole interactions 3. hydrogen bond

Question 70

The weakest of intermolecular interactions are the dispersion forces, known as ________ forces.

Answer 70

London

Question 71

Electron density is unequally distributed between 2 atoms in any given moment, resulting in rapid polarization and counterpolarization of the e- cloud and the formation of short-lived dipole moments. These dipoles are generated with neighboring molecules as well. What type of IMF is this?

Answer 71

London dispersion forces | weakest because they shift constantly

Question 72

The next weakest after London forces are ________-________ interactions, which are of intermediate strength.

Answer 72

dipole-dipole

Question 73

Polar molecules tend to orient themselves so that the oppositely charged ends of the respective molecular dipoles are closest to each other: the positive region of one molecule is close to the negative region of another molecules. Denoted by dashed lines. What IMF is this?

Answer 73

dipole-dipole interactions | present in solids and liquids, not gas (too far apart)

Question 74

Polar species tend to have (lower/higher?) melting and boiling points because of dipole-dipole interactions.

Answer 74

higher

Question 75

Finally, the strongest type of interaction is the ____________ bond.

Answer 75

hydrogen | not actually a bond - no sharing or transfer of e-

Question 76

Hydrogen bonds are an unusually strong form of ________-________ interaction that can be ________- or ____________. What types of molecules is it common to see this?

Answer 76

dipole-dipole; intra or intermolecular Common in biochemical molecules, especially water!

Question 77

When hydrogen is bonded to 1 of 3 highly EN atoms, the H atom carries only a small amount of e- density in the covalent bond. What 3 atoms? | Hydrogen bonds, pick up the **FON** (phone)

Answer 77

Fluorine, oxygen, nitrogen

Question 78

# Hydrogen bonds The positively charged hydrogen atom interacts with the partial negative charge of fluorine, oxygen, or nitrogen on nearby molecules. The H atom acts like a naked ________

Answer 78

proton

Question 79

Substances that display hydrogen bonding tend to have unusually (low/high?) boiling points compared to compounds of similar molecular weights that do not exhibit H bonding.

Answer 79

high