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General Chemistry > Chapter 3 - Bonding and Chemical Reactions > Flashcards

Chapter 3 - Bonding and Chemical Reactions Flashcards

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1
Q

what is a covalent bond?

A

atoms share electrons; attraction that each electron in the shared pair has for the two positive nuclei of the bonded atoms

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2
Q

what are characteristics of molecules with covalent bonds?

A

lower melting and boiling points, poor conductors of electricity

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3
Q

what are single, double, and triple bonds?

A

Two atoms sharing one, two, or three pairs of electrons are said to be joined by a single, double, or triple bond

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4
Q

what is bond order?

A

the number of shared electron pairs (ie. bond order of a single bond is 1)

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5
Q

what is bond length?

A

average distance between two nuclei of atoms in a bond

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6
Q

how does bond length change

A

as number of pairs of shared electrons increases, the two atoms are pulled closer together; triple bond shorter than double bond, which is shorter than a single bond

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7
Q

what is bond energy?

A

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

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8
Q

how does bond energy change?

A

greater the number of pairs of electrons shared between the two atoms, the more energy required to break the bonds holding the atoms together; triple bonds have greatest bond energy, single bonds have lowest bond energy; greater the bond energy, the stronger the bond

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9
Q

when does polarity occur?

A

when two atoms have relative differences in electronegativity, the atom with the larger electronegativity gets the larger share of electron density

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10
Q

what is a nonpolar covalent bond?

A

when atoms that have identical or nearly identical EN share electron pairs, they do so with equal distribution of the electrons; EN difference of 0.5 or less, no separation of charges

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11
Q

what are the diatomic molecules?

A

H, O, F, Br, I, N, Cl

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12
Q

what is a polar covalent bond?

A

atoms that differ moderately in their EN will share electrons unevenly, difference in EN between 0.5-1.7

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13
Q

what is a partial positive charge?

A

occurs when less electronegative atom takes on less of the electron density

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14
Q

what is a partial negative charge?

A

occurs when the more electronegative atom takes on more of the electron density

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15
Q

what makes a polar molecule?

A

separation of positive and negative charges

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16
Q

what is the equation for a dipole moment?

A

p=qd (charge x distance)

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17
Q

what is a coordinated covalent bond?

A

both of the shared electrons originated on the same atom; lone pair of one atom attacks another atom with an unhybridized p-orbital; typically found in Lewis acid-base reactions

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18
Q

what are bonding electrons?

A

electrons involved in a covalent bond

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19
Q

what are nonbonding electrons?

A

electrons in the valence shell that are not involved in covalent t bonds, aka lone pairs

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20
Q

what is a Lewis structure?

A

system of notation developed to keep track of bonded and nonbonded electron pairs

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21
Q

what is formal charge?

A

difference between the number of valence electrons of each atom and the number of electrons the atom is associated with

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22
Q

what is the equation for formal charge?

A

FC= # of valence electrons in atom – number of bonds- nonbonded electrons

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23
Q

what is the assumption made by formal charge?

A

Assumes equal sharing of all bonded electron pairs regardless of actual differences between EN

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24
Q

what is a lewis dot diagram?

A

chemical symbol of element surrounded by dots, each representing one of the s or p valence electrons

25
Q

what are resonance structures?

A

two or more Lewis structures that demonstrate the same arrangement of atoms but differ the specific placement of the electrons, represented with a double headed arrow between them

26
Q

what is a resonance hybrid?

A

actual electronic distribution in the compound is a hybrid or the possible resonance structures (more stable a structure, the more it contributes to a resonance hybrid)

27
Q

what makes a structure more stable?

A
  • lewis structure with small or no formal charges is preferred over a Lewis structure with large formal charges
  • lewis structure with less separation between opposite charges is preferred over a Lewis structure with a large separation of opposite charges
  • lewis structure in which negative formal charges are placed on more electronegative atoms is more stable than one in which the negative formal charges are placed on less electronegative atoms
28
Q

what is valence shell electron pair repulsion theory (VSEPR)?

A

uses Lewis dot structures to predict the molecular geometry of covalently bonded molecules, 3D arrangement of atoms is determined by the repulsion between bonding and nonbonding electron pairs in the valence shell of the central atom, arrange themselves as far apart as possible, minimizing repulsive forces

29
Q

what are electronic geometries?

A

are concerned only with the basic geometry (just with the steric number, not differentiating between bonding and non-bonding electrons) ie. Electronic geometry of water is tetrahedral, not bent

30
Q

what are molecular geometries?

A

are concerned with the actual specific geometry, which includes the nonbonding vs. bonding electrons; ie. Molecular geometry of water is bent

31
Q

what is steric number?

A

number of bonded species (not bond order!!, triple bond is 1) and number and electron pairs on the central atom

32
Q

what determines the ideal bond angle?

A

the electronic geometries?

33
Q

what exerts more repulsion - bonding electrons or nonbonding electrons

A

nonbonding electrons

34
Q

what happens to bond angle as nonbonding electrons increase?

A

the bond angle decreases

35
Q

molecular geometry: steric #2

A

linear

36
Q

molecular geometry: steric #3, no lone pairs

A

trigonal planar

37
Q

molecular geometry: steric #3, 1 lone pair

A

bent

38
Q

molecular geometry: steric #4, no lone pairs

A

tetrahedral

39
Q

molecular geometry: steric #4, 1 lone pair

A

trigonal pyramidal

40
Q

molecular geometry: steric #4, two lone pairs

A

bent

41
Q

molecular geometry: steric #5, no lone pairs

A

trigonal bipyramidal

42
Q

molecular geometry: steric #5, one lone pair

A

seesaw

43
Q

molecular geometry: steric #5, two lone pairs

A

T-shaped

44
Q

molecular geometry: steric #5, three lone pairs

A

linear

45
Q

molecular geometry: steric #6, no lone pairs

A

octahedral

46
Q

molecular geometry: steric #6, one lone pair

A

square pyramidal

47
Q

molecular geometry: steric #6, two lone pairs

A

square planar

48
Q

molecular geometry: steric #6, three lone pairs

A

T-shaped

49
Q

molecular geometry: steric #4, four lone pairs

A

linear

50
Q

what is the ideal bond angle of steric #2?

A

180

51
Q

what is the ideal bond angle of steric #3?

A

120

52
Q

what is the ideal bond angle of steric #4?

A

109.5

53
Q

what is the ideal bond angle of steric #5?

A

90 and 120

54
Q

what is the ideal bond angle of steric #6?

A

90

55
Q

when is a compound nonpolar?

A

compound only has nonpolar bonds, or compound has polar bonds but the molecular geometry is in such a way that the dipole moments cancel each other out

56
Q

when is a compound polar?

A

when the molecular geometry is arranged such that the bond dipoles do not cancel each other out

57
Q

what is a molecular orbital?

A

• when two atoms bond to form a compound, the atomic orbitals interact to form a molecular orbital, which describes the probability of finding the bonding electrons in a given space; obtained by combining wave functions of the atomic orbitals
o if signs of the two atomic orbitals are the same a bonding orbital forms
o if the signs are different, an antibonding orbital forms

58
Q

what is a sigma bond?

A

when orbitals overlap head to head, allows free rotation about their axes

59
Q

what is a pi bond?

A

when orbitals overlap so that there are two parallel electron cloud densities, does not allow for free rotation

General Chemistry (7 decks)

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