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

Topic 4: Chemical Bonding and Structure Flashcards

(68 cards)

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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
trional planear
120 - 3 electron domains - 3 bonding electrons, 0 non bonding electrons e.g. boron fluoride
26
special bent/vshaped
105 (104.5) 4 electron domains - 2 bonding, 2 non bonding electron pairs e.g. water
27
tetrahedral
109.5 4 electron domains 4 bonding electrons, 0 non bonding e.g. methane
28
trigonal pyramidal
107 4 electron domains 3 bonding, 1 non bonding e.g. Nitrous acid
29
what is the polarity of a molecule determined by?
- polar bonds of the molecule | - shape and symmetry of the molecule
30
resonance
- 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
benzene
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
giant moleculear crystalline
giant molecular/network covalent/macromolecular structure | -single molecule with repeating patterns of covalent bonds
33
silicon bonding
- each silicon atom bonded to 4 others in tetrahedral arrangement; forms silicon cyrstal structure
34
carbon allotropes
different forms of an element in a physical state; in this case carbon
35
graphite bonding
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
graphite electrical conductivity
good electrical conductivity; 1 non bonded delocalized electron per atom allows for electron mobility
37
graphite thermal conductivity
weak thermal conductor | - unless heat can be forced to conduct in parallel direction
38
graphite apperance and physical properties
- non lustrous - grey crystalline solid - soft and slippery sheets due to slippage of layers over each other - brittle
39
graphite mt. and bp. points
high meting and boiling point
40
graphite uses
can be used as dry lubricant pencils electrode rods in electrolysis
41
diamond bonding + structure
each C atom is covalently bonded to 4 others in tetrahdral arrangement in regular repettitive pattern with 109.5 bond angles
42
diamond electrical conductivity
non conductor of electricity | - all electrons bonded; non mobile
43
diamond thermal conductivity
efficent thermal conductor | high melting and boiling points
44
diamond physical properties and apperance
highl transparent, lustrous crystals, hardest known substance - brittle - hard to scratch
45
diamond uses
jewllery ornamants tools machines for cutting glass
46
fullerene bonding and structure
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
fullerene electrical conductivity
semi-conductor at normal temperature and pressure | - some electron mobility as it accepts electrons to form anions
48
fullerene thermal conductivity
low thermal conductivity | low melting point
49
fullerene physical properties and apperance
yellow crystaline solid benzene soluble light and strong; react with potassium to make superconducting crystalline moleucles
50
fullerene uses
lubrciant medical and industrial uses for binding and reaction nanotubules catalyst
51
graphene bonding and structure
each c atom covalently bonded to 3 others to form hexagon with 1209 bond angles - single layer (2D chicken wire construction)
52
graphene electrical conductivity
good conductivity; one delocalized electon per atom
53
graphene thermal conductivity
best thermal conductor
54
graphene physical properties and appearance
``` almost completly transparent one atom thick strong flexbile high melting point thinnest matieral ```
55
graphene uses
``` TEM grids photovolatic cells touch screen tech solar panels supercapacitators nanotechnoogy ```
56
london dispersion forces
(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
dipole to dipole forces
- 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
hydrogen bonding
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
intermolecular forces?
van der waal (london dispersion forces, dipole to dipole, hydrogen bonding)
60
trends in intermolecular forces (melting and boiling point)
stronger forces= harder to seperate molecules | increasing forces result in increasing Mt. an Bp. points
61
trends in intermolecular forces (solubility)
"like dissolves like' non polar in non polar polar in polar
62
trends in intermolecular forces (electrical conductivity)
covalent compounds have no ions dont conduct electrons polar covalent molecules can in water
63
metallic bond
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
what is the strength of a metallic bond determined by?
- number of delocalized electrons - charge on cation - radius of cation
65
alloy
solutions of metals with enhanced properties | -metals are added together so different ions mix
66
alloy examples
steel (iron and carbon) stailness steel (iron, nickle, chromium) brass (copper and zinc) bronze (copper and strontium(
67
metallic bond properties
- 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
silicon dioxide
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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