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DAT > Chemistry Chemical Bonding > Flashcards

Chemistry Chemical Bonding Flashcards

1
Q

Many molecules contain atoms bonded according to the octet rule, which states that an atom tends to bond with other atoms until it has eight electrons in its outermost shells, thereby forming a stable ___ similar to that of the noble gas neon

A

electron configuration

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2
Q

In ___, one or more electrons from an atom with a smaller ionization energy are transferred to an atom with a greater electron affinity, and the resulting ions are held together by electrostatic forces

A

ionic bonding

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3
Q

In covalent bonding, an ___ is shared between two atoms

A

covalent bonding

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4
Q

When two atoms with large differences in electronegativity react, there is a complete transfer of electrons from the less ___ to the more electronegative atom

A

electronegative atom

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5
Q

Often, more than one Lewis structure can be drawn for a ___; this phenomenon is called resonance

A

molecule

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6
Q

When different atoms interact to form a bond, only their outermost regions come in contact. Hence, only the ___ are involved

A

valence electrons

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7
Q

A Lewis dot symbol contains the symbol of an element and one “dot” for each valence electron in an atom. Magnesium belongs to Group IIA and has two valence electrons (:Mg). Note that, because the transitional metals, lanthanides, and actinides all have incompletely filled inner shells, ___ are not written for these elements

A

Lewis dot symbols

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8
Q

Certain steps must be followed in assigning a Lewis structure to a molecule.
1. Count all the ___ of the atoms. The number of valence electrons of the molecule is the sum of the valence electrons of all atoms present:
H has 1 valence electron;
C has 4 valence electrons;
N has 5 valence electrons; therefore,
HCN has a total of 10 valence electrons

A

valence electrons

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9
Q

Step Two in assigning a Lewis structure to a ___ involves writing the skeletal structure of the compound (i.e., the arrangement of atoms). In general, the least electronegative atom is the central atom. Hydrogen (always) and the halogens F, Cl, Br, and I (usually) occupy the end positions. Draw single bonds between the central atom and the atoms surrounding it, placing an electron pair in each bond (bonding electron pair)
In HCN, H must occupy a terminal position. Of the remaining two atoms, C is the less electronegative and therefore occupies the central position. The skeletal structure is as follows:
H:C:N
Each bond has 2 electrons so 10-4 = 6 valence electrons remain

A

molecule

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10
Q

Step Three of Lewis structure construction involves ___ the octets (8 valence electrons) of all atoms bonded to the central atom, using the remaining valence electrons still to be assigned. (Recall that H is an exception to the octet rule since it can only have only 2 valence electrons.) With HCN, H already has 2 valence electrons in its bond with C

A

completing

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11
Q

Step Four of Lewis structure construction involves placing any extra electrons on the central atom. If the central atom has less than an octet, try to write double or triple bonds between the central and surrounding atoms using the nonbonding, unshared lone electron pairs. The HCN structure above does not satisfy the octet rule for C because C possesses only 4 valence electrons. Therefore, 2 lone electron pairs from the N atom must be moved to form two more ___ with C, creating a triple bond between C and N

A

bonds

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12
Q

Step Five of Lewis structure construction involves drawing bonds as lines rather than pairs of ___. Now the octet rule is satisfied for all three atoms because C and N have 8 valence electrons and H has 2 valence electrons

A

dots

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13
Q

The number of ___ officially assigned to an atom in a Lewis structure does not always equal the number of valence electrons of the free atom

A

valence electrons

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14
Q

The difference between the number of electrons officially assigned to an atom and the valence electrons of the free atom is the ___ of the atom. Formal charge has many uses in chemistry, including predicting which of several possible Lewis structures is the most likely. Specifically, the structure with the lowest formal charges tends to best represent the molecule. Formal charge can be calculated using the following formula:
Formal charge = V -(1/2)*N sub bonding - N sub nonbonding

A

formal charge

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15
Q

Formal charge = V - (1/2)*N sub bonding - N sub nonbonding
V is the number of valence electrons in the free atom, N sub bonding is the number of bonding ___, and N sub nonbonding is the number of nonbonding electrons.
Using a Lewis dot structure, where 2 bonding electrons are represented by a stick and each nonbonding electron is represented with a dot, the formal charge is also represented by:
Formal charge = V - (# of sticks + # of dots)

A

electrons

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16
Q

The formal charge of an ion or ___ is equal to the sum of the formal charges of the individual atoms comprising it

A

molecule

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17
Q

For some molecules, two or more non-identical Lewis structures can be drawn; these arrangements are called ___ structures

A

resonance

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18
Q

A ___ is one of two or more Lewis structures for a single molecule unable to be described fully with only one Lewis structure

A

resonance structure

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19
Q

The actual molecule is a hybrid of these (three in the case of SO2) structures (spectral data indicate that the two SO bonds are identical). This phenomenon is known as resonance, and the actual structure of the molecule is called the ___. Resonance structures are expressed with a double-headed arrow between them

A

resonance hybrid

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20
Q

A Lewis structure with small or no ___ is preferred over a Lewis structure with large formal charges (the previous contributes to the character of the resonance hybrid)

A

formal charges

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21
Q

A Lewis structure in which negative formal charges are placed on more ___ is more stable than one in which the negative formal charges are placed on less electronegative atoms

A

electronegative atoms

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22
Q

Atoms found in or beyond the third period can have more than eight ___, since some of the valence electrons may occupy d orbitals. These atoms can be assigned more than four bonds in Lewis structures

A

valence electrons

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23
Q

The Lewis structure of the sulfate ion, SO4 2- can be drawn in six ___ by alternating the placement of pi electrons. Giving sulfur 12 valence electrons permits three of the five atoms to be assigned a formal charge of zero, which is most favorable energetically

A

resonance forms

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24
Q

___ occurs between atoms with small differences in electronegativity, generally in the range of 0.4 to 1.7 Pauling units. The bonding electron pair is not shared equally but is pulled more toward the element with the higher electronegativity. As a result, the more electronegative atom acquires a partial negative charge, delta negative, and the less electronegative atom acquires a partial positive charge, delta positive, giving the molecule a partially ionic character

A

polar covalent bonding

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25
Q

A molecule that has such a separation of positive and negative ___ is called a polar molecule

A

charges

26
Q

The ___ is a measure of the polarity of a molecule. It is a vector quantity mu, measured in Debye units (coulomb-meters) and defined as the product of the charge magnitude (q) and the distance between the two partial charges (r):
mu = qr

A

dipole moment

27
Q

___ occurs between atoms that have the same electronegativities

A

nonpolar covalent bonding

28
Q

With ___, the bonding electron pair is shared equally such that there is no separation of charge across the bond. Nonpolar covalent bonds occur in diatomic molecules such as H2, Cl2, O2, and N2

A

nonpolar covalent bonding

29
Q

In a ___, the shared electron pair comes from the lone pair of one of the atoms in the molecule

A

coordinate covalent bond

30
Q

Once such a ___ forms (coordinate covalent bond), it is indistinguishable from any other covalent bond, so identifying such a bond is useful only in keeping track of the valence electrons and formal charges

A

bond

31
Q

A ___ is a compound that can accept an electron pair to form a covalent bond; a Lewis base is a compound that can donate an electron pair to form a covalent bond

A

lewis acid

32
Q

The ___ theory uses Lewis structures to predict the molecular geometry of covalently bonded molecules

A

valence shell electron-pair repulsion (VSEPR)

33
Q

VSEPR theory states that the three-dimensional arrangement of atoms surrounding ___ is determined by the repulsions between the bonding and the nonbonding electron pairs in the valence shell of the central atom

A

central atom

34
Q

These bonding and nonbonding electron pairs arrange themselves as far apart as possible, thereby ___ repulsion

A

minimizing

35
Q

The following steps are used to predict the ___ of a molecule using the VSEPR theory:

  1. Draw the Lewis structure of the molecule
  2. Count the total number of bonding and nonbonding electron pairs in the valence shell of the central atom
  3. Arrange the electron pairs around the central atom o that they are as far apart from each other as possible
  4. Determine the bond angle, accounting for the additional repulsion due to nonbonding electrons, which pushes any bonding pairs slightly closer together
A

geometric structure

36
Q

A molecule with nonpolar bonds is always nonpolar; a molecule with polar bonds may be polar or nonpolar depending on the orientation of the ___ dipoles

A

bond

37
Q

A ___ with two atoms bound by a polar bond must have a net dipole moment and therefore be polar

A

molecule

38
Q

A molecule consisting of more than two atoms bound with ___ may be either polar or nonpolar since the overall dipole moment of a molecule is the vector sum of the individual bond dipole moments

A

polar bonds

39
Q

If the molecule has a particular ___ such that the bond dipole moments cancel each other (i.e., if the vector sum is zero), then the result is a nonpolar molecule

A

shape

40
Q

Formally, molecular orbitals are obtained by adding the wave functions of the atomic orbitals. Qualitatively, this is described by the overlap of two atomic orbitals. If the two ___ are in phase with each other, a bonding orbital is formed. If the two atomic orbitals are completely out of phase with each other, an antibonding orbital is formed

A

atomic orbitals

41
Q

When two orbitals of different atoms ___ head-to-head, the resulting bond is called a sigma bond.

A

overlap

42
Q

When ___ p orbitals interact, a pi bond is formed

A

parallel

43
Q

In order of decreasing ___, attractive forces that exist between molecules are as follows:
dipole-ion > hydrogen bonding > dipole-dipole > LDF

A

strength

44
Q

Those ___ not due to the interactions of ions or hydrogen bonding (i.e., dipole-dipole and LDF) are also collectively referred to as van der Waals forces

A

forces

45
Q

Evaluating intermolecular ___ is most import for determining melting and boiling points

A

forces

46
Q

Stronger intermolecular forces hold ___ together more tightly, so more energy (generally represented by higher temperatures) is required to weaken those bonds to allow for phase changes

A

molecules

47
Q

___ interactions are present in the solid and liquid phases but become negligible in the gas phase because the molecules are generally much farther apart

A

dipole-dipole

48
Q

___ tend to have higher boiling points than nonpolar species of comparable molecular weight

A

polar species

49
Q

Hydrogen bonds: ___ up the FON (phone): Hydrogen bonds exist in molecules containing a hydrogen bonded to Fluorine, Oxygen, or Nitrogen

A

pick

50
Q

___ is a specific, particularly strong form of dipole-dipole interaction

A

hydrogen bonding

51
Q

When hydrogen is bound to either fluorine, oxygen, or nitrogen, the hydrogen atom carries little of the electron density of the ___ bond. This positively charged hydrogen atom interacts with the partial negative charge located on the electronegative atoms of nearby molecules.

A

covalent

52
Q

___ between the delta positive on the H and the delta negative on the nearby molecule is the hydrogen bond

A

interaction

53
Q

Substances that display hydrogen bonding tend to have unusually high ___ compared with compounds of similar molecular weight that do not hydrogen bond

A

boiling points

54
Q

The bonding electron in ___ may appear to be shared equally between two atoms, but, at any particular point in time, they will be located randomly throughout the orbital

A

covalent bonds

55
Q

Bonded ___ may appear to be shared equally but may be located randomly throughout the orbital permits unequal sharing of electrons, causing rapid polarization and counterpolarization of the electron cloud and formation of short-lived dipoles

A

electrons

56
Q

When polarization and counterpolarization of the ___ takes place, these dipoles interact with the electron clouds of neighboring molecules, inducing the formation of more dipoles. The attractive interactions of these short-lived dipoles are called London dispersion forces (LDF)

A

electron clou

57
Q

Dispersion forces are generally weaker than other ___ forces

A

intermolecular

58
Q

___ do not extend over long distances and are therefore most important when molecules are close together

A

dispersion forces

59
Q

The strength of a dispersion force depends directly on how easily the electrons in the ___ can move (i.e., be polarized)

A

molecules

60
Q

Large molecules in which the __ are far from the nucleus are relatively easy to polarize and therefore possess greater dispersion forces

A

electrons

61
Q

If not for dispersion forces, the ___ would not liquefy at any temperature since no other intermolecular forces exist between the noble gas atoms

A

noble gases

62
Q

The ___ at which the noble gases liquefy is to some extent indicative of the magnitude of dispersion forces between the atoms

A

low temperature

DAT (46 decks)

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