Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry IB HL (2016+) > Topic 4: Chemical Bonding and Structure > Flashcards

Topic 4: Chemical Bonding and Structure Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

why do chemicals bond?

A

to achieve stability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

ionic bond

A

AKA electrovalent bond

  • the sum of all electrostatic attractions and repulsions in the ionic compound
  • established by the transfer of electrons from one atom to another
  • to form ions with complete valence shells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

conditions for the formation of ionic bonds

A
  • no of valence electrons
  • formation of ionic bonds is exothermic due to electron transfer and bond formation
  • big diff in electronegativity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

nature of ionic bonds

A
  • solid ionic compounds held in crystal lattice

- ↑ lattice energy = ↑ ionic bond strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

characteristics of ionic compounds

A
  • high m.pt/b.pt: bonds require a lot of energy to break
  • solids at room temp: due to strong electrostatic forces of attraction between locked ions in crystal lattice
  • brittle: ions of the same charge are beside each other, so the repulsive forces cause it to split
  • soluble in water: as water is a polar solvent, it detaches ions from the crystal lattice due to its electrostatic pull
  • good conductors in molten state: as ions are free to move about
  • low volatility
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

covalent bond

A
  • bond formed by mutual sharing of electrons between the combining atoms
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

conditions for covalent bond

A
  • must have 5-7 valence e-s
  • equal electronegativity (so no transferring of electrons occurs)
  • equal electron affinity to equally attract the electron pair
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

covalent bonding parameters

A
  • bond length
  • bond angle
  • bond energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

bond length

A

avg. distance between centres of nuclei of 2 bonded atoms

unit: picometer (pm)/angstrom (Å)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

factors affecting bond length

A
  • bond multiplicity: ↑ no. of bonds (i.e. single/double/etc), ↓ bond length
  • atom size: ↑ size, ↑ bond length
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

bond energy

A
  • energy required to break one mole of covalently bonded atoms in gaseous state
  • measures bond strength
    unit: kJ/mol
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

factors affecting bond energy

A
  • bond length: ↑ length, ↓ bond energy

- size of bonded atom: ↑ size, ↓ bond energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

coordinate (dative) bonds

A
  • type of covalent bond

- both electrons in the shared pair of e-s come from the same atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

polar covalent bond

A
  • covalent bond in which electrons are shared unequally
  • due to unequal electronegativity
  • thus bonded atoms acquire a partial positive/negative charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

VSEPR Theory

A

Valence Shell Electron Pair Repulsion Theory

  • electron pairs tend to repel each other
  • pairs try to stay as far apart to have min. energy and max. stability
  • greater repulsion between non-bonded e-s
  • the geometry of a molecule is dependent on the no. of valence e-s around the central atom
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

resonance structure

A

when the molecule’s characteristic properties can be described by 2+ structures, the real structure is a resonance hybrid of the possible structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

allotrope

A
  • different forms of the same element

- they have differing physical properties but similar chemical properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

allotropes of carbon

A
  • diamond
  • graphite
  • fullerene (C60)
  • graphene
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

structure of diamond

A
  • giant 3-D covalent tetrahedral arrangement
  • each C is strongly bonded to 4 other Cs (tetrahedral)
  • no plane of weakness
  • all bonds are equally strong
  • electrons can’t move freely
  • so diamond can’t conduct electricity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

uses of diamond

A
  • cutting glass
  • making bores for rock drilling
  • grinding/polishing hard materials
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

structure of graphite

A
  • consists of 2-D hexagonal rings
  • each C atom is strongly bonded to 3 other Cs
  • weak Van der Waal forces between layers
  • layers can slide over each other so graphite is an excellent lubricant
  • graphite can also conduct electricity due to delocalized e-s, making it a good conductor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

uses of graphite

A
  • making electrodes
  • lubricant
  • pencil lead
23
Q

structure of fullerene

A
  • perfect sphere
  • consisting of 60 C atoms arranged in hexagonal and pentagonal rings
  • soluble in suitable organic solvents
  • forms coloured solutions in organic solvents (varying from red to brown to magenta)
  • has delocalised e-s but doesn’t conduct electricity
24
Q

uses of fullerene

A
  • ferromagnetism

- super conductivity

25
Q

graphene

A
  • very thin: 1 atom thick!
  • 200x stronger than steel
  • single planar sheet of hexagonally-arranged C-atoms (similar to graphite in this sense)
  • excellent thermal and electrical conductivity (300x efficiency of copper)
  • a 1mm thick piece consists of 3 million stacked sheets
  • forms a carbon nanotube when rolled up
  • when rolled up more, becomes fullerene
26
Q

types of intermolecular forces

A
  • London dispersion forces
  • dipole-dipole forces
  • hydrogen bonding
  • ionic bonding
  • covalent bonding
  • metallic bonding
27
Q

order of bond strength

A

ionic bonds > hydrogen bonds > dipole-dipole > London forces

28
Q

types of van der waals forces

A
  • London dispersion forces

- dipole-dipole forces

29
Q

London dispersion forces

A
  • weakest intermolecular force
  • existing in all covalent compounds
  • ↑ ease of polarisation = ↑ strength of London dispersion forces
  • caused by temporary dipole due to random electron movement
  • has inductive effect on neighbouring molecules
30
Q

factors affecting London forces

A
  • no. of e-s: ↑ no. of e-s = ↑ distance between valence e-s and nucleus = ↓ attraction to nucleus = ↑ ease of polarisation
  • size of e- cloud: ↑ size = ↑ ease of polarisation
  • shape of molecule: ↓ branching = ↑ ease of polarisation
31
Q

polarisability

A

the ease of distortion of the electron cloud of a molecule by an electric field

32
Q

dipole-dipole force

A
  • slightly stronger than London dispersion forces
  • occurs due to electrostatic attraction between molecules with permanent dipoles
  • exists in all polar molecules with permanent dipole movement
  • b.pt increases significantly
33
Q

hydrogen bond

A
  • result of interaction
  • between un-bonded e- pair on one atom and a H atom in a different molecule that carries a high partial positive charge
  • due to the H atom being bonded to a small, highly electronegative element (e.g. O, N, F)
  • thus it’s literally just a proton and the e- pair is attracted to it
34
Q

effect of H-bonding on b.pt

A
  • hydrogen bonds are strong dipole-dipole interactions
  • in Group 5, 6, and 7: hydrogen bonding causes m.pt&raquo_space;» compared to dipole-dipole bonding in other hydrides of that group
  • can be seen with water, HF, and NH3
35
Q

Silicon Dioxide (SiO2), Quartz

A
  • 3-D tetrahedral covalent network (just like diamond)

- each Si atom is covalently bonded to 4 O atoms, and each O atom is covalently bonded to 2 Si atoms

36
Q

properties of silicon dioxide

A
  • insoluble in water

- doesn’t conduct electricity in solid state

37
Q

solubility rules

A
  • polar substances dissolve more easily in polar solvents (same rule applies to non-polar substances)
  • in organic molecules: ↑ length of chain = ↓ solubility to water
38
Q

factors determining m.pt/b.pt

A
  • bond strength
  • impurities
  • structure
39
Q

metallic bonding

A

the electrostatic forces of attraction between the lattice of cations and the delocalised sea of electrons

40
Q

factors affecting metallic bond strength

A
  • no. of delocalised e-s: ↑ no. of delocalized e-s = ↑ bond strength
  • charge on cation: ↑ charge = ↑ bond strength
  • cation radius: ↑ radius = ↓ bond strength
41
Q

properties of metallic compounds

A
  • good conductors
  • shiny/lustrous: due to delocalised electrons reflecting light
  • high m.pt/b.pt
  • malleable (i.e. can be reshaped under pressure)
  • ductile (i.e. can be drawn out in a wire)
42
Q

why are metals malleable and ductile?

A
  • the close-packed cation layers can slide over each other

- and they can do so without breaking more bonds than are made

43
Q

chemical bond

A

an attractive force that acts between 2 or more atoms to hold them together as a stable molecule

44
Q

exceptions to octet rule

A
  • elements before 3rd period may not fulfil octet rule
  • elements on and after 3rd period may exceed octet rule
  • because elements on and after 3rd period have d-orbitals
45
Q

what is the electron domain/negative charge centre in VSEPR?

A
  • double or triple bonded e-s are oriented together
  • they behave as a single unit in terms of repulsion
  • this is known as the electron domain/negative charge centre
46
Q

what is the order of repulsion in VSEPR theory?

A

Lp-Lp > Lp-Bp > Bp-Bp
Lp = lone pair
Bp = bond pair

  • when a molecule has lone pairs of e-s, the bonding e- pairs are pushed closer
  • because the lone pair is free moving
  • but bond pairs are not, they must remain in the region between 2 atoms
  • this decreases Bp’s bond angle
47
Q

formal charge

A

no of atom valence e-s (according to periodic table) - no of valence e-s in a specified molecule (only includes 1 e- from each bond)
- ideally formal charge should be as close to 0 as possible!

48
Q

common alloys

A
  • brass
  • bronze
  • solder
  • pewter
  • amalgam
49
Q

components of brass

A 
principal metal: copper
added metal(s): zinc
50
Q

components of bronze

A 
principal metal: copper
added metal(s): tin
51
Q

components of solder

A 
principal metal: lead
added metal(s): tin
52
Q

components of pewter

A 
principal metal: tin
added metal(s): can be copper, antimony, bismuth, or lead
53
Q

components of amalgam

A 
principal metal: mercury
added metal(s): can be tin, silver, gold, or sodium

Chemistry IB HL (2016+) (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions