T4: Bonding Flashcards

1
Q

metallic structure

A

giant lattice (regular arrangement of particles)

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2
Q

metallic bonding

A

strong metallic bonds

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3
Q

metallic structure and bonding definition

A

strong electrostatic attraction between positive metal ions surrounded by a sea of delocalised electrons

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4
Q

comparing the strength of metallic bonds (the bonding in Mg is stronger than in Na)

A
  • Mg2+ has a greater charge of 2+
  • Mg2+ ions are smaller
  • attraction between the Mg2+ ions and the delocalised e- is stronger
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5
Q

properties of metals conductivity

A

they have delocalised e-

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6
Q

properties of metals strength of the metal

A

strong electrostatic attraction between the positive metal ions and delocalised e-

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7
Q

properties of metals malleable and ductile

A

layers of metal ions can slide past one another

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8
Q

properties of metals melting and boiling points

A

strength of the metallic bonds

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9
Q

covalent structure

A

macromolecular or simple molecular

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10
Q

covalent bonding

A

strong covalent bonds

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11
Q

covalent structure and bonding definition

A

a shared pair of electrons between 2 atoms

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12
Q

How does sharing e- hold atoms together

A

The attraction forces are stronger than the repulsion forces and therefore the atoms are held together

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13
Q

3 macromolecular structures

A
  • carbon
  • silicon
  • silicon dioxide
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14
Q

2 macromolecular crystals

A
  • diamond
  • graphite
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15
Q

diamond characteristics

A
  • each C has 4 covalent bonds
  • tetrahedral shape
  • very high mp
  • very hard
  • non-conductor
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16
Q

graphite characteristics

A
  • layers with 3 covalent bonds to each C
  • high mp
  • each C has delocalised e-
  • layers held together by weak intermolecular forces
  • soft layers can slide over each other
  • conductor (has delocalised e-)
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17
Q

examples of simple molecular structures

A

H2O (water)
NH3 (ammonia)
Cl2 (chlorine)
O2 (oxygen)
CH4 (methane)

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18
Q

example of drawing simple molecular structure (I2)

A

3 molecules each with 2 atoms covalently bonded with intermolecular forces between the molecules

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19
Q

forces and properties of simple molecular structures

A
  • intermolecular forces act between molecules
  • simple molecular substance boils intermolecular forces break
  • intermolecular forces weaker than covalent bonds so simple molecular compounds have low mp
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20
Q

ionic structure

A

giant lattice

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21
Q

ionic bonding

A

strong ionic bonds

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22
Q

ionic structure and bonding definition

A

an ionic bond is the strong electrostatic attraction between oppositely charged ions

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23
Q

drawing the structure of an ionic compound

A
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24
Q

physical properties of ionic compounds high mp + bp

A

strong electrostatic attraction

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25
Q

physical properties of ionic compounds electrical conductivity

A

solid -> ions fixed in lattice so cannot move
aqueous / molten -> ions can now move and conduct electricity

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26
Q

structural properties tend to be brittle + shatter easily

A

when an external force is applied the layers of ions shift and like charges repel causing the crystal to crack

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27
Q

molecule definition

A

a group of atoms which are covalently bonded to 1 another

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28
Q

coordinate bond definition

A

a shared electron pair which have both come from the same atom

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29
Q

covalent bond =

A

bonded pair

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30
Q

coordinate bond =

A

lone pair

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31
Q

model ans lone pair donation question

A

lone pair of electrons on the X+ / X- is donated to Y

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32
Q

valence definition

A

the outer shell of electrons (e- used in bonding)

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33
Q

to minimise their (bonding and lone pairs) repulsion…

A

the e- pairs repel each other as far apart as possible

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34
Q

strength of repulsion between lone and bonding pairs equation

A

lone pair to lone pair > lone pair to bond pair > bond pair to bond pair

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35
Q

strength of repulsion between lone and bonding pairs

A
  • lone pairs repel more than bonding pairs
  • the strength of the repulsions determines the bond angles between the bond to bond pairs
36
Q

VSEPR theory - draw the shapes of molecules and ions, name them and give the bonding angles

A
37
Q

electronegativity definition

A

the power of an atom to attract the pair of electrons in a covalent bond

38
Q

which element has the highest electronegativity

A

F - 4.0

39
Q

what are the next elements with the highest electronegativity

A

O - 3.5
N - 3.0
Cl - 3.0
Br - 2.8
I - 2.5
S - 2.5
P - 2.1

40
Q

the 3 factors which determine how electronegative elements are

A
  • nuclear charge
  • atomic radius
  • shielding
41
Q

elements with high electronegativity have…

A
  • high nuclear charge
  • relatively low atomic radius
  • low amount of shielding
42
Q

(EN) covalent bonding =

A

small difference in EN

43
Q

(EN) ionic bonding =

A

large difference in EN

44
Q

across Period 2 the EN increases because…

A
  • number of protons increase
  • same shielding
  • ability to attract electrons in a covalent bond increases
45
Q

polarity in Cl2

A

Molecules made of atoms with no difference in EN have their electrons distributed evenly
Bond = non polar

46
Q

polarity in HCl

A

Bond is unsymmetrical
1 atom that is more EN
H (δ+) - Cl (δ-)
This creates what’s called a ‘dipole’

47
Q

polarity of BF3 (molecule)

A
  • Molecule is symmetrical
  • Dipoles cancel out
  • NON-POLAR
48
Q

polarity of NH3 (molecule)

A
  • Molecule is not symmetrical
  • Dipoles don’t cancel out
  • POLAR
49
Q

polarity of CHCl3 (molecule)

A
  • Molecule is not symmetrical
  • Dipoles don’t cancel out
  • POLAR
50
Q

where do imf found

A

between molecules

51
Q

3 intermolecular forces

A
  • H bonding
  • permanent dipole-dipole
  • induced dipole-dipole (van der waals forces)
52
Q

how do you know if it has H bonding

A

H bonded to F, N, O

53
Q

how do you know if it has permanent dipole dipole forces

A
  • not H bonded to F, N, O
  • polar molecule
54
Q

how do you know if it has induced dipole dipole forces (van der waals forces)

A
  • not H bonded to F, N, O
  • non-polar molecule
55
Q

what happens to the stronger intermolecular forces

A
  • have a higher mp + bp
  • more energy to overcome the imf
56
Q

what is special about I2 (imf)

A
  • i.d.d forces
  • large molecule (lots of e-)
  • solid at room temp
  • stronger imf than H bonding in water
57
Q

BF3 (identifying imf)

A
  • non-polar
  • i.d.d forces between molecules
  • least energy required to overcome forces between molecules
58
Q

NH3 (identifying imf)

A
  • H bonding between molecules
  • strongest attraction between molecules
59
Q

CHCl3 (identifying imf)

A
  • polar
  • p.d.d between molecules
60
Q

bp comparison (how to write it)

A

NH3 > CHCl3 > BF3

61
Q

H bonding when it occurs

A
  • strongest intermolecular attraction
  • occurs between H (bonded to N, O, F) and a lone pair on a N, O, F atom on another molecule
62
Q

H bonding how does it arise

A
  • N, O, F are highly electronegative
  • there is large difference in electronegativity between O + H (state atoms) creates a dipole on O-H bond (state bond)
  • lone pair on O atom (state atom) in 1 molecule strongly attracts a partially positive H atom on another molecule
63
Q

H bonding how to draw it

A
64
Q

P.D.D forces when it occurs

A
  • generally weaker than H bonding
  • occurs between polar molecules
65
Q

P.D.D forces how does it arise

A
  • difference in EN leads to bond polarity
  • dipoles do not cancel out therefore the molecule has an overall permanent molecule
  • there is an attraction between δ+ on 1 molecule and δ- on another
66
Q

P.D.D forces how to draw it

A
67
Q

I.D.D forces when it occurs

A
  • generally weakest force (stronger than H and PDD if large molecular)
  • occurs between all molecules (and atoms of noble gases) important force in non-polar molecules - don’t have any other i.m.f
68
Q

I.D.D forces how does it arise

A

(RUTID)
R -> Random movement of e- in 1 molecule (atom) leads to an…
U -> Uneven distribution of e-, creating a…
T -> Temporary dipole in 1 molecule (atom). This…
I -> Induces a induced dipole in a neighbouring molecules (atom)
D -> Dipole attract

69
Q

I.D.D forces how to draw it

A
70
Q

i.m.f in molecules containing H
(graph shows bp of molecules changes as the central atoms get bigger)
key points to note from the graph

A
  • H2O, HF, NH3 all have H bonding between molecules
  • other molecules increase in bp as size increases
  • bigger molecules have stronger I.d.d forces between molecules
71
Q

The importance of H bonding in ice

A

Ice less dense than water
H bonds in ice hold the molecules further apart

72
Q

The importance of H bonding in proteins

A

Proteins held in complex 3D shapes by H bonds
N-H group on 1 amino acid and H bonding to the C=O group on another

73
Q

the importance of H bonding in DNA

A
  • 2 strands double helix DNA held by H bonds
  • H bonds strong enough to hold strands together
  • weak enough to enable DNA helix to separate for DNA replication when cells divide
74
Q

physical properties of period 3 elements (trends in mp and bp) -> what 3 things should you talk about

A

1 Na to Mg to Al
2 Silicon
3 P, S, Cl and Ar

75
Q

phosphorus chemical formula

A

P4

76
Q

silicon chemical formula

A

S8

77
Q

chlorine chemical formula

A

Cl2

78
Q

argon chemical formula

A

Ar

79
Q

physical properties of period 3 elements (trends in mp and bp) -> Na to Mg to Al

A

mp increases Na to Mg to Al as strength of metallic bonding increases
Na only forms +1 ions, Mg forms +2 ions, Al forms +3 ions
Na ions are largest whereas Al ions are smallest so stronger metallic bonding for Al

80
Q

physical properties of period 3 elements (trends in mp and bp) -> Silicon

A
  • high mp -> macromolecular -> held by strong covalent bonds that require lots of energy to break
81
Q

physical properties of period 3 elements (trends in mp and bp) -> P, S, Cl and Ar

A
  • simple molecular -> I.D.D increase for bigger molecules
  • S8 biggest strongest VdW higher mp and bp
  • P4 next in size order slightly lower mp and bp
  • Cl2 smallest of 3 weakest VdW lowest mp and bp
  • Ar single atoms weakest VdW forces of non-metals lowest mp and bp of all period 3 elements
82
Q

physical properties of period 3 elements (trends in mp and bp) -> silicon has the highest mp but aluminium has the highest bp

A

Si strong covalent bonds -> high temp needed once
Molten relatively little more energy is then needed to vapourise it -> bp not much higher then the mp
compared to Al once molten a lot of energy is still needed to overcome strong electrostatic metallic bonds -> Al has very high bp

83
Q

comparison question 1

A
  • Br is simple molecular
  • Mg is metallic
  • Br has weak VdW forces between molecules
  • more energy is needed to overcome the stronger metallic bonds
  • Mg has a much greater liquid range because forces of attraction in liquid are stronger
84
Q

comparison question 2

A

HCl -> p.d.d between molecules
I2 -> i.d.d between molecules
I2 is a bigger molecule so stronger i.d.d forces between molecules

85
Q

comparison question 3 [6m]

A

HF -> simple molecular -> H bonding between molecules -> strongest attraction of 3 -> requires most energy to break

CH3Cl -> simple molecular -> p.d.d forces between molecules

Ne -> simple atomic -> i.d.d forces between atoms -> weakest attraction of the 3 -> requires least energy to break