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Gen Chem 1 > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

bonds

A

forces that hold groups of atoms together

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2
Q

bond energy

A

energy required to break a bond

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3
Q

bond length

A

distance between 2 atoms when potential energy is minimal

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4
Q

ionic

A

taking of e- from one atom to another
-example: Na+ Cl- (takes an e-)

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5
Q

covalent

A

equal or almost equal e- sharing
- example: C-C, C-H

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6
Q

polar covalent bond

A

unequal sharing of electrons
- example: H-F (hydrogen is more electropositive and fluorine is mor electronegative)

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7
Q

electronegativity

A

ability of an atom in a molecule to attract shared electrons to itself

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8
Q

what is the equation for difference between actual and expected bond energies

A

difference= (H-X)actual - (H-X)expected

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9
Q

what happens to the difference when H and X have identical electronegativities

A
  • difference is 0
  • (H-X)actual and (H-X)expected are the same
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10
Q

what happens when X has a greater electronegativity than H

A

shared electrons will tend to be closer to the X
- molecule will be polar with a partial + charge on the H and a partial - charge on the X

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11
Q

what is the pattern for electronegativity

A
  • as you move from left to right on the periodic table, the EN increases
  • as you move down from top to bottom of the periodic table, the EN decreases
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12
Q

hydrogen electronegativity

A

2.1

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13
Q

carbon electronegativity

A

2.5

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14
Q

oxygen electronegativity

A

3.5

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15
Q

fluorine electronegativity

A

4.0

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16
Q

francium electronegativity

A

0.7

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17
Q

what is the EN difference for covalent bond type

A

difference EN: 0-0.4
- electronegativity difference in binding atoms: zero

18
Q

what is the EN difference for polar covalent bond type

A

difference EN: 0.5-1.9
- EN difference in binding atoms: intermediate

19
Q

what is the EN difference in ionic bond type

A

difference in EN: >2.0
- EN difference in bonding atoms: large

20
Q

which of the following elements forms ionic bonds with chlorine
K
Al
P
Kr
Br

A

need lowest electronegative element; greatest difference in EN
K

21
Q

dipole moment

A
  • molecules that have a center of positive charge and a center of negative charge
  • vector sum of bond polarities
  • example= water (2 bonds)
22
Q

vector

A

value with both a magnitude and a direction

23
Q

bond polarities

A

localized bond electronegativities

24
Q

what happens when bond polarity increases

A
  • difference in EN increases
  • dipole moment increases
25
Q

what happens when difference in EN decreases

A

decrease in dipole moment

26
Q

how does dipole moment work in other molecules

A
  • have polar bonds but not have a dipole moment
  • the dipoles will cancel out
  • example: CO2
27
Q

which of the following is most polar bond without being considered ionic
C-O
Mg-O
O-O
N-O
O-F

A

C-O; difference= 1.0
most polar need to have greatest difference in EN

28
Q

what happens when a metal and nonmetal react

A

atom results in a noble gas like electron configuration
- done through valence electrons

29
Q

what are some factors that influence ionic size

A
  • relative sizes of an ion and its parent atom
  • position of parent element in periodic table
30
Q

what is usually the pattern of sizes of ion and parent atom

A

(+) ions are smaller than parent and (-) ions are larger than parent

31
Q

how does the ion size trend work

A

ion sizes increase down a group

32
Q

isoelectronic ions

A
  • ions with same # of electrons
  • trend= size decreases as nuclear charge (Z) increases
33
Q

lattice energy

A

gives us an idea about the strength of the ionic bond
- change in energy from separated gaseous ions to ionic solid from
- energy released (-) when an ionic solid forms from its ions

34
Q

what is the generic equation for lattice energy

A

M+ (g) + X- (g) —> MX (s)

35
Q

what is the lattice energy calculations

A

K(Q1Q2/r)
k- proportionality constant
Q1 & Q2- charges on the ions
r- shortest distance between the centers of anions and cations

36
Q

greater the charges, what happens to lattice energy

A

greater the lattice energy

37
Q

shorter the distance, what happens to lattice energy

A

greater the lattice energy

38
Q

example of lattice energy calculation

A

LiF
(+1) x (-1)= -1

39
Q

percent ionic character of a bond

A

(measured dipole moment of X-Y/calculated dipole moment of X+Y-) x 100%

40
Q

how can element be classified as ionic

A

any compound that conducts an electric current

41
Q

what do many substances contain

A

polyatomic ions
- bonds within ions are covalent

42
Q

what is the relationship between ionic character and EN difference

A

ionic character increases with EN difference
- none of the bonds reach 100% ionic character
- no individual bons are completely ionic

Gen Chem 1 (3 decks)

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