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AP chem > Chem Terms Ch 8 > Flashcards

Chem Terms Ch 8 Flashcards

1
Q

Bond Enthalpy

A

Energy NEEDED to break a covalent bond

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2
Q

Breaking bonds require energy

A

Ending
Delta H is positive

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3
Q

Forming bonds releases energy

A

Exo
Delta H is negative

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4
Q

Can use average ____ values to estimate enthalpies of reactions in which bonds are broken and new bonds are formed

A

Bond enthalpy

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5
Q

Covalent bonding is like

A

A tug of war over electrons

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6
Q

Nonpolar covalent bond

A

Perfectly equal sharing of e-

  1. Diatomic molecules
  2. Carbon - hydrogen (C-H) bond
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7
Q

Polar covalent bond

A

Unequal sharing of e- due to electronegativity differences

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8
Q

Electronegativity

A

How much an atom wants an e- when it’s in a covalent bond

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9
Q

Because e- are shared ____ in ____ partial charges exist

A

Unequally, polar bonds

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10
Q

Formal charge

A

The charge that each atom would have in a molecule if e- were shared equally

Used to pick the “best” Lewis structure when multiple exist

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11
Q

Calculating formal charge

A
  1. All unshared e- on an atom are assigned e-
  2. Half of the shared e- are assigned e-

Formal charge = valence e- - assigned e-

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12
Q

The best structure has….

A
  1. Formal charges closest to zero
  2. (Only if 1 doesn’t pick it) the negative formal charge on most electronegative atom
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13
Q

Resonance

A

Bond length can be measured and single, double, and triple bonds have different lengths

e- are not locked into place, they are resonating, “real picture” is an average of what it occurring

Resonance : moving back and forth

Avg. bond = # of bonds / # of places

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14
Q

Octet exceptions

A
  1. Odd number of electrons
  2. Less than an octet (most often occurs with Be and B)
  3. More than an octet (expanded octet)
    *occurs only if there are close by d orbitals
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15
Q

Strength of covalent bonds, bond length, and bond disassociation energy

A

Bond dissociation energy ⬇️
Bond strength ⬇️
Bond length ⬆️

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16
Q

Ionic bond

A

Force existing between ions of opposite charge, transfer of e-

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17
Q

Ionic compounds are stable:

A

Attraction of opposite charges draws ions together, releasing energy upon bond formation, results in a solid lattice

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18
Q

Lattice energy

A

Energy required to completely separate a mol of an ionic substance into its gaseous ions

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19
Q

Lattice energy depends on…

A
  1. Ion charges
  2. Distance between charges

*depends primarily on ion charges

Lattice energy ⬆️ as ion charges ⬆️ as distance ⬇️

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20
Q

Electronegativity

A

How much an atom wants an e- when it’s bonded to something else

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21
Q

Covalent bonding

A

2 nonmetals share e-

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22
Q

Lewis structures

A

2-d pictures that show the sharing of e-

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23
Q

Lewis Structures: Rules for drawing

A
  1. Count total valence e-
  2. Arrange atoms

a. If 2 atoms, place side by side
b. If C, goes in center
c. The least electronegative atom in center

  1. Add in valence e- on atoms
  2. From bond (2 e-)
  3. Count and check
    a. Octet rule
    b. Total valence e-

Hydrogen never in center

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24
Q

Unshared e-

A

Lone pairs

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25
Q

Shared e-

A

Single bond

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26
Q

Single bond:

Double bond:

Triple Bond:

A

2 e-

4 e-

6 e-

27
Q

Bond polarity

A

Unequal sharing of e- caused by electronegativity differences

28
Q

Dipole moment

A

Caused by partial charges from unequal e- sharing

29
Q

Vector quantities

A

Both a magnitude (size) AND a direction

30
Q

For a molecule that consists of more than ____ atoms, the dipole movement depends on both ____ of the individual bonds and the geometry of the molecule

A

Two, the polarities

31
Q

VSEPR model

A

Valence Shell Electron Pair Repulsion

e- groups repel one another and want to be far apart

Strive for largest bond angle possible

32
Q

Bonding pair

33
Q

Nonbonding pair (lone pair)

A

Assigned to one atom

34
Q

Electron domain

A

Bonding e- + lone pairs on control atom

Trick: double or triple bond counts as 1e- domain

35
Q

Electron - domain geometry

A

Determined by # of domains on central atom

Ex: tetrahedral

36
Q

Molecular geometry

A

The geometry of only the atoms in a molecule (taking into account that lone pairs cause repulsion)

Ex: trigonal pyramid

37
Q

Bond angles ____ as lone pairs on central atom ____

A

Decreases, increase

38
Q

Bonding pair of e- are attracted to ___ nuclei

39
Q

Lone pair is only attracted to ___ nucleus

40
Q

Lone pairs/ no bonding experience less nuclear attraction and spread out more (take up ___ space)

41
Q

Multiple bond exerts a ____ repulsive force, causing single bonds to move away

42
Q

VSEPR can be ____ for larger molecules

43
Q

Carbon always bonds ___[ times

44
Q

Like dissolved in like

A

Polar dissolves in polar
Nonpolar dissolves in Nonpolar
Polar does NOT dissolve in Nonpolar

45
Q

Soluble =

46
Q

Shortcomings of VSEPR

A

Predicts shape, does not account for why/how bonds exist between atoms

2 ideas: atomic orbitals and Lewis structures = valence bond theory

47
Q

Lewis structures

A

Atoms share e- (e- density between nuclei)

48
Q

Lewis structures

A

Atoms share e- (e- density between nuclei)

49
Q

Valence bond theory

A

Merging of atomic orbitals

50
Q

Orbital overlap

A

Orbitals share a region of space

51
Q

Always an optimal distance for overlap

52
Q

Hybrid

53
Q

To explain the why behind VSEPR…

A

We mix atomic orbitals together to form hybrid orbitals; process is called HYBRIDIZATION

54
Q

HUGE connection between hybrid orbitals and five main geometries

A

Linear
Trig. Planar
Tetrahedral
Trig. Bypyramid
Octahedral

55
Q

To form 2 identical bonds Be needs 2 unpaired identical e-

56
Q

Initially forming hybrid orbitals require E, but when bonds form a HUGE E release occurs

A

“Investments”

57
Q

Overlap occurs along intranuclear axis

A

Sigma bond

58
Q

Overlap occurs along or below inter nuclear axis

59
Q

Sigma is ___ than PI bonds

60
Q

All single bonds are

61
Q

A double bond has

A

Sigma and Pi bond

62
Q

Triple bond is

A

One sigma, and two PI bonds

63
Q

Localized bonding

A

Shared e- between only two atoms

64
Q

Delocalized bonding

A

In structures with resonance, the e- are shared between more than 2 atoms due to resonating behavior

AP chem (8 decks)

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