T4: Bonding Flashcards
1
Q
metallic structure
A
giant lattice (regular arrangement of particles)
2
Q
metallic bonding
A
strong metallic bonds
3
Q
metallic structure and bonding definition
A
strong electrostatic attraction between positive metal ions surrounded by a sea of delocalised electrons
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
5
Q
properties of metals conductivity
A
they have delocalised e-
6
Q
properties of metals strength of the metal
A
strong electrostatic attraction between the positive metal ions and delocalised e-
7
Q
properties of metals malleable and ductile
A
layers of metal ions can slide past one another
8
Q
properties of metals melting and boiling points
A
strength of the metallic bonds
9
Q
covalent structure
A
macromolecular or simple molecular
10
Q
covalent bonding
A
strong covalent bonds
11
Q
covalent structure and bonding definition
A
a shared pair of electrons between 2 atoms
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
13
Q
3 macromolecular structures
A
- carbon
- silicon
- silicon dioxide
14
Q
2 macromolecular crystals
A
- diamond
- graphite
15
Q
diamond characteristics
A
- each C has 4 covalent bonds
- tetrahedral shape
- very high mp
- very hard
- non-conductor
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-)
17
Q
examples of simple molecular structures
A
H2O (water)
NH3 (ammonia)
Cl2 (chlorine)
O2 (oxygen)
CH4 (methane)
18
Q
example of drawing simple molecular structure (I2)
A
3 molecules each with 2 atoms covalently bonded with intermolecular forces between the molecules
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
20
Q
ionic structure
A
giant lattice
21
Q
ionic bonding
A
strong ionic bonds
22
Q
ionic structure and bonding definition
A
an ionic bond is the strong electrostatic attraction between oppositely charged ions
23
Q
drawing the structure of an ionic compound
A
24
Q
physical properties of ionic compounds high mp + bp
A
strong electrostatic attraction
25
physical properties of ionic compounds electrical conductivity
solid -> ions fixed in lattice so cannot move
aqueous / molten -> ions can now move and conduct electricity
26
structural properties tend to be brittle + shatter easily
when an external force is applied the layers of ions shift and like charges repel causing the crystal to crack
27
molecule definition
a group of atoms which are covalently bonded to 1 another
28
coordinate bond definition
a shared electron pair which have both come from the same atom
29
covalent bond =
bonded pair
30
coordinate bond =
lone pair
31
model ans lone pair donation question
lone pair of electrons on the X+ / X- is donated to Y
32
valence definition
the outer shell of electrons (e- used in bonding)
33
to minimise their (bonding and lone pairs) repulsion...
the e- pairs repel each other as far apart as possible
34
strength of repulsion between lone and bonding pairs equation
lone pair to lone pair > lone pair to bond pair > bond pair to bond pair
35
strength of repulsion between lone and bonding pairs
- lone pairs repel more than bonding pairs
- the strength of the repulsions determines the bond angles between the bond to bond pairs
36
VSEPR theory - draw the shapes of molecules and ions, name them and give the bonding angles
37
electronegativity definition
the power of an atom to attract the pair of electrons in a covalent bond
38
which element has the highest electronegativity
F - 4.0
39
what are the next elements with the highest electronegativity
O - 3.5
N - 3.0
Cl - 3.0
Br - 2.8
I - 2.5
S - 2.5
P - 2.1
40
the 3 factors which determine how electronegative elements are
- nuclear charge
- atomic radius
- shielding
41
elements with high electronegativity have...
- high nuclear charge
- relatively low atomic radius
- low amount of shielding
42
(EN) covalent bonding =
small difference in EN
43
(EN) ionic bonding =
large difference in EN
44
across Period 2 the EN increases because...
- number of protons increase
- same shielding
- ability to attract electrons in a covalent bond increases
45
polarity in Cl2
Molecules made of atoms with no difference in EN have their electrons distributed evenly
Bond = non polar
46
polarity in HCl
Bond is unsymmetrical
1 atom that is more EN
H (δ+) - Cl (δ-)
This creates what's called a 'dipole'
47
polarity of BF3 (molecule)
- Molecule is symmetrical
- Dipoles cancel out
- NON-POLAR
48
polarity of NH3 (molecule)
- Molecule is not symmetrical
- Dipoles don't cancel out
- POLAR
49
polarity of CHCl3 (molecule)
- Molecule is not symmetrical
- Dipoles don't cancel out
- POLAR
50
where do imf found
between molecules
51
3 intermolecular forces
- H bonding
- permanent dipole-dipole
- induced dipole-dipole (van der waals forces)
52
how do you know if it has H bonding
H bonded to F, N, O
53
how do you know if it has permanent dipole dipole forces
- not H bonded to F, N, O
- polar molecule
54
how do you know if it has induced dipole dipole forces (van der waals forces)
- not H bonded to F, N, O
- non-polar molecule
55
what happens to the stronger intermolecular forces
- have a higher mp + bp
- more energy to overcome the imf
56
what is special about I2 (imf)
- i.d.d forces
- large molecule (lots of e-)
- solid at room temp
- stronger imf than H bonding in water
57
BF3 (identifying imf)
- non-polar
- i.d.d forces between molecules
- least energy required to overcome forces between molecules
58
NH3 (identifying imf)
- H bonding between molecules
- strongest attraction between molecules
59
CHCl3 (identifying imf)
- polar
- p.d.d between molecules
60
bp comparison (how to write it)
NH3 > CHCl3 > BF3
61
H bonding when it occurs
- 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
H bonding how does it arise
- 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
H bonding how to draw it
64
P.D.D forces when it occurs
- generally weaker than H bonding
- occurs between polar molecules
65
P.D.D forces how does it arise
- 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
P.D.D forces how to draw it
67
I.D.D forces when it occurs
- 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
I.D.D forces how does it arise
(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
I.D.D forces how to draw it
70
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
- 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
The importance of H bonding in ice
Ice less dense than water
H bonds in ice hold the molecules further apart
72
The importance of H bonding in proteins
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
the importance of H bonding in DNA
- 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
physical properties of period 3 elements (trends in mp and bp) -> what 3 things should you talk about
1 Na to Mg to Al
2 Silicon
3 P, S, Cl and Ar
75
phosphorus chemical formula
P4
76
silicon chemical formula
S8
77
chlorine chemical formula
Cl2
78
argon chemical formula
Ar
79
physical properties of period 3 elements (trends in mp and bp) -> Na to Mg to Al
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
physical properties of period 3 elements (trends in mp and bp) -> Silicon
- high mp -> macromolecular -> held by strong covalent bonds that require lots of energy to break
81
physical properties of period 3 elements (trends in mp and bp) -> P, S, Cl and Ar
- 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
physical properties of period 3 elements (trends in mp and bp) -> silicon has the highest mp but aluminium has the highest bp
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
comparison question 1
- 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
comparison question 2
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
comparison question 3 [6m]
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
