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MCAT General Chemistry > Chapter 3: Bonding and Chemical Interactions > Flashcards

Chapter 3: Bonding and Chemical Interactions Flashcards

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1
Q

Which element?

____________ can only have 2 valence electrons.

A

Hydrogen

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2
Q

Which elements?

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

A

Lithium and beryllium

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3
Q

Which element?

________ bonds to attain 6 valence electrons.

A

Boron

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4
Q

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

A

3; d

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5
Q

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).

A

incomplete

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6
Q

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.

A

expanded

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7
Q

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.

A

cannot

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8
Q

Which 6 elements almost always abide the octet rule?

A
  1. carbon
  2. nitrogen
  3. oxygen
  4. fluorine
  5. sodium
  6. magnesium
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9
Q

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

typically metal to nonmetal

A

ionic

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10
Q

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

A

The electrostatic attraction between opposite charges; lattice

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11
Q

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

A

covalent

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12
Q

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

A

polarity

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13
Q

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 ________________ ____________.

A

nonpolar; polar; coordinate covalent

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14
Q

Unlike ionic crystal lattices, covalent compounds consist of what?

A

Individually bonded molecules

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15
Q

________ bonds form between atoms that have significantly different electronegativies.

A

ionic

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16
Q

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

A

cations; anions

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17
Q

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

A

shared; transferred

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18
Q

What value?

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

A

1.7

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19
Q

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

A

very high

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20
Q

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

A

dissolve; conductors

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21
Q

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

A

maximized, minimized

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22
Q

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.

A

electronegativities

instead, they share electrons

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

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23
Q

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

A

weak

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24
Q

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

A

bond order

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

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25
Q

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

A

bond length

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26
Q

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

A

The 2 atoms are pulled closer together and bond length decreases

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27
Q

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

A

bond energy

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28
Q

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

A

more

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29
Q

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

A

stronger

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30
Q

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

A

polarity

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31
Q

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!!

A

dipole

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32
Q

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

A

nonpolar covalent

no separtion of charge

33
Q

What are the 7 common diatomic molecules?

A
  1. H2
  2. N2
  3. O2
  4. F2
  5. Cl2
  6. Br2
  7. I2
34
Q

What value?

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

A

0.5

35
Q

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

A

polar covalent

36
Q

The difference in EN should be between ____ and ____.

A

0.5 and 1.7

37
Q

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

A

separation

38
Q

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

A

dipole moment

39
Q

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

A

p = qd

p = dipole moment
q = magnitude of charge
d = displacement

Equation 3.1

40
Q

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

A

Debye units - coulomb meters

41
Q

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.

A

coordinate covalent

42
Q

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

A

Lewis acid-base

43
Q

A Lewis acid is any compound that ________________.

A

accepts a lone pair of e-

44
Q

A Lewis base is any compound that ________________.

A

donates a pair of e-

45
Q

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

A

bonding; nonbonding

46
Q

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

A

lone

47
Q

Formal charge is what? How is it calculated?

A

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

Formal charge = valence electrons - dots - sticks

48
Q

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

A

Lewis

49
Q

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

A

minimizes

50
Q

Each dot on a Lewis dot diagram represents what?

A

an s or p valence electron of an atom

51
Q

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

A

electronegative

52
Q

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

A

underestimate; overestimate

in oxidation state, we assume the more EN atom has 100% of the bonding e- share

53
Q

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.

A

resonance structures

54
Q

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

A

character

55
Q

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

A

small/ no

56
Q

A Lewis structure with ____ separation between opposite charges is preferred

A

less

57
Q

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

A

more

58
Q

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

A

Electronic

most important for ideal bond angle

59
Q

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

A

Molecular

main focus of MCAT

60
Q

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

A

coordination

61
Q

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

A

more

62
Q

A compound with nonpolar bonds is always ________.

A

nonpolar

63
Q

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

A

nonpolar

usually symmetrical

64
Q

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.

A

molecular

65
Q

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

A

wave functions

66
Q

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

A

bonding; antibonding

67
Q

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.

A

sigma

68
Q

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.

A

pi

69
Q

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

A
  1. London dispersion forces
  2. dipole-dipole interactions
  3. hydrogen bond
70
Q

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

A

London

71
Q

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?

A

London dispersion forces

weakest because they shift constantly

72
Q

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

A

dipole-dipole

73
Q

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?

A

dipole-dipole interactions

present in solids and liquids, not gas (too far apart)

74
Q

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

A

higher

75
Q

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

A

hydrogen

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

76
Q

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

A

dipole-dipole; intra or intermolecular

Common in biochemical molecules, especially water!

77
Q

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)

A

Fluorine, oxygen, nitrogen

78
Q

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 ________

A

proton

79
Q

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.

A

high

MCAT General Chemistry (12 decks)

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