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IB CHEMISTRY 2017 EXAM > Topic 4: Chemical Bonding and Structure > Flashcards

Topic 4: Chemical Bonding and Structure Flashcards

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1
Q

Ion

A

an ion is a charged particle. Ions form from (groups of) atoms by the loss or gain of one or more electrons

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2
Q

Ionic bond

A

electrostatic attraction between oppositley charged ions

form when opositely charged ions attract (e.g nonmetal and a metal)

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3
Q

ionic compounds

A

have a lattice structure (3D chrystalline)

  • fixed arrangement of ions based on repeating unit; have low volatility
  • e.g. coordination number of NaCl lattice is 6 because each sodium ion surrounded by 6 chloride ions and vice versa
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4
Q

lattice energy

A

measure of the strength of attraction between ions in their lattice

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5
Q

volatility of ionic compounds

A

low volatility (tendency of a substance to vaporize)

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6
Q

solubility of ionic compounds

A
  • determined by the degree to which separated particles of solute are able to form bonds/attractive forces with the solvent
    = solubility depends on nature of solvent (‘like dissolves like’)
    -ionic compounds are generally soluble in ionic/polar solvents but not in non-polar solvents
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7
Q

boiling/melting point of ionic compounds

A

high melting and boiling points

  • strong electrostatic force attraction between ions
  • solid at room temperature
  • the higher the ion charge, the higher the mt and bp points
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8
Q

electrical and thermal conductivity of ionic compounds

A

don’t conduct electricity in solid state;

conduct in molten state or in an aqueous solution (due to free, delocalized electrons that can move)

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9
Q

physical properties of ionic compounds

A

BRITTLE; movement of ions of the same charge along each other causes repulsive forces to cause them to split

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10
Q

how do you make an ionic compound?

A
  • reactive metal and non metal (cation and anion)

1. 8+ electronegativity difference between compounds (extent of ionic character)

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11
Q

covalent bond

A

electrostatic attraction between a pair of electrons and a postivley charged nuclei

  • sharing of electrons
  • nonmetal and nonmetal
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12
Q

molecule

A

a group of atoms held together by a covalent bond
- contains a fixed numbef of atoms
2 atoms=diatomic= Cl2 or O2

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13
Q

octet rule

A

when atoms react, they tend to achieve an outer shell with 8 electrons in order to form stability (full shell)

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14
Q

bond length…

A

measure of distance between two bonded nuclei

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15
Q

bond strength…

A

measure of enthalpy required to break bonds

strong bonds are short bonds

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16
Q

polar bonds

A

unsymetrical/unequal sharing of electrons

  • dipole; two separated opposite electric charges of a bond
  • can be determined by electronegativity difference ( over 0.4; polar)
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17
Q

pure covalent

A

when electronegativity is equal to 0; bonds between the same atoms

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18
Q

covalent structures

A

lewis diagrams show valence shell structures

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19
Q

coordinate bond

A

when both shared electrons from from one atom

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20
Q

exeptions to octet rule

A

BeCl2, H2 and BF3 (electron deficient atoms)

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21
Q

VSEPR theory

A

because electron pairs in the same valence shells carry the same charge, they repel each other so they spread themselves as far apart as possible
electron domain; all electron locations in the valence shell

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22
Q

repulsions

A

stronger repulsions on lone pairs

weaker repulsiosn on bonding pairs

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23
Q

linear

A

180
2 bonding electron pairs
0 non bonding electron pairs
2 electron domains

e.g. carbon dioxide

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24
Q

bent/v-shaped

A

less than 120 (117)

  • 3 electron domains
  • 2 bonding, 1 non ponding electron pair

e.g. silicon dioxide

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25
Q

trional planear

A

120

  • 3 electron domains
  • 3 bonding electrons, 0 non bonding electrons

e.g. boron fluoride

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26
Q

special bent/vshaped

A

105 (104.5)
4 electron domains
- 2 bonding, 2 non bonding electron pairs

e.g. water

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27
Q

tetrahedral

A

109.5
4 electron domains
4 bonding electrons, 0 non bonding

e.g. methane

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28
Q

trigonal pyramidal

A

107
4 electron domains
3 bonding, 1 non bonding

e.g. Nitrous acid

29
Q

what is the polarity of a molecule determined by?

A
  • polar bonds of the molecule

- shape and symmetry of the molecule

30
Q

resonance

A
  • delocalized bonds that can be in multiple positions
  • results in more than one valid lewis structure (true structure is the average)
  • bond enthalpy value often between a single and double bond
  • e.g. triatomic oxygen where multiple representations are valid
31
Q

benzene

A

hexagonal ring C6H6
kekules dream
trigonal planear arrangmenent of 120 bond angles
resonant structure
bond length and enthalpy between single and double bond
circle represents the delocalized electrons

32
Q

giant moleculear crystalline

A

giant molecular/network covalent/macromolecular structure

-single molecule with repeating patterns of covalent bonds

33
Q

silicon bonding

A
  • each silicon atom bonded to 4 others in tetrahedral arrangement; forms silicon cyrstal structure
34
Q

carbon allotropes

A

different forms of an element in a physical state; in this case carbon

35
Q

graphite bonding

A

most stable allotrope;
each C is covalently bonded to 3 others
- hexagons in parallel layers with 120 bonds
- weak london dispersion forces; layers can slide over another

36
Q

graphite electrical conductivity

A

good electrical conductivity; 1 non bonded delocalized electron per atom allows for electron mobility

37
Q

graphite thermal conductivity

A

weak thermal conductor

- unless heat can be forced to conduct in parallel direction

38
Q

graphite apperance and physical properties

A
  • non lustrous
  • grey crystalline solid
  • soft and slippery sheets due to slippage of layers over each other
  • brittle
39
Q

graphite mt. and bp. points

A

high meting and boiling point

40
Q

graphite uses

A

can be used as dry lubricant
pencils
electrode rods in electrolysis

41
Q

diamond bonding + structure

A

each C atom is covalently bonded to 4 others in tetrahdral arrangement in regular repettitive pattern with 109.5 bond angles

42
Q

diamond electrical conductivity

A

non conductor of electricity

- all electrons bonded; non mobile

43
Q

diamond thermal conductivity

A

efficent thermal conductor

high melting and boiling points

44
Q

diamond physical properties and apperance

A

highl transparent, lustrous crystals, hardest known substance

  • brittle
  • hard to scratch
45
Q

diamond uses

A

jewllery
ornamants
tools
machines for cutting glass

46
Q

fullerene bonding and structure

A

each C atom bonded in sphre to 60 carbon atoms

  • 12 pentagons
  • 20 hexagons
  • closed spherical cage with each c atom bonded to 3 others
47
Q

fullerene electrical conductivity

A

semi-conductor at normal temperature and pressure

- some electron mobility as it accepts electrons to form anions

48
Q

fullerene thermal conductivity

A

low thermal conductivity

low melting point

49
Q

fullerene physical properties and apperance

A

yellow crystaline solid
benzene soluble
light and strong; react with potassium to make superconducting crystalline moleucles

50
Q

fullerene uses

A

lubrciant
medical and industrial uses for binding and reaction
nanotubules
catalyst

51
Q

graphene bonding and structure

A

each c atom covalently bonded to 3 others to form hexagon with 1209 bond angles
- single layer (2D chicken wire construction)

52
Q

graphene electrical conductivity

A

good conductivity; one delocalized electon per atom

53
Q

graphene thermal conductivity

A

best thermal conductor

54
Q

graphene physical properties and appearance

A 
almost completly transparent
one atom thick
strong
flexbile
high melting point
thinnest matieral
55
Q

graphene uses

A 
TEM
grids
photovolatic cells
touch screen tech
solar panels 
supercapacitators 
nanotechnoogy
56
Q

london dispersion forces

A

(weakest form of attraction)

  • instantaneous dipole-dipole induced forces that exist between any atoms
  • electrons are mobile clouds of negative charge that are constnalty forming creating induced dipoles by their instantenous dipoles
  • occurs between opposite ends; of these 2 temporary dipoles
  • strengh increases with molecular size as more electrons avaialble
  • only force that exists in non polar molecule
  • correlation to boilding point
57
Q

dipole to dipole forces

A
  • in polar molecules
  • permament seperation of charge within the bonds as a result of different electronegativities (permanent dipole)
  • permanent dipoles of molecules attract other molecules by hydrogen bonding
  • the more polar a substance, the higher the bp
58
Q

hydrogen bonding

A

type of dipole to dipole
strongest form of attraction
hydogen directly bonds to F, N, O (highly electronegative element) between moleucles e.g. water
- make boiliding point of a substanec higher

59
Q

intermolecular forces?

A

van der waal (london dispersion forces, dipole to dipole, hydrogen bonding)

60
Q

trends in intermolecular forces (melting and boiling point)

A

stronger forces= harder to seperate molecules

increasing forces result in increasing Mt. an Bp. points

61
Q

trends in intermolecular forces (solubility)

A

“like dissolves like’
non polar in non polar
polar in polar

62
Q

trends in intermolecular forces (electrical conductivity)

A

covalent compounds have no ions
dont conduct electrons
polar covalent molecules can in water

63
Q

metallic bond

A

electrostatic attraction between a lattice of positive ions and a sea of delocalized electrons
metal + metal
metal atoms withotu electrons from a lattic of positive ions in a pod of delocalized electrons

64
Q

what is the strength of a metallic bond determined by?

A
  • number of delocalized electrons
  • charge on cation
  • radius of cation
65
Q

alloy

A

solutions of metals with enhanced properties

-metals are added together so different ions mix

66
Q

alloy examples

A

steel (iron and carbon)
stailness steel (iron, nickle, chromium)
brass (copper and zinc)
bronze (copper and strontium(

67
Q

metallic bond properties

A
  • good electrical conductivity (circuits)
  • good thermal conductivity; cooking
  • malleable; moved into structures
  • ductile; wires and cables
  • high melting point; tools
  • shiny and lustrous; ornaments
68
Q

silicon dioxide

A

quartz; forms a giant covalent structure based on tetrahederal arrangement

  • each Si atom boned covalently to 4 oxygen atoms
  • each oxygen atom bonded to 2 silicon atoms
  • strong
  • insoluble in water
  • high melting point
  • nonconductor of electricity

IB CHEMISTRY 2017 EXAM (12 decks)

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