Structure and Bonding Flashcards
1
Q
What is metallic bonding?
A
The electrostatic force of attraction between positively charged ions and declocalised electrons.
2
Q
What is meant by delocalised electrons?
A
The electrons in the outer shell of metal atom move freely through the atoms in the lattice.
3
Q
Why do metals conduct electricity?
A
Because of the free moving electrons, the delocalised electrons
4
Q
What does the structure of metals consist of?
A
a giant lattice of positively charged ions and declocalised electrons
5
Q
What is ionic bonding?
A
the electrostatic attraction between the positive ions of one element (usually metals) and the negative ions of another element (usually non-metals).
6
Q
What does the structure of ionic compounds consist of?
A
giant lattice of oppositely charged ions
7
Q
How do atoms form ionic bonds and by doing so what do they achieve?
A
by giving away or receiving electrons. By doing so they achieve a stable electron arrangement .
8
Q
What is covalent bonding?
A
The electrostatic force of attraction between two positive nuclei and a shared pair of electrons
9
Q
What is a covalent bond the result of?
A
two positive nuclei being held together by their attraction for a shared pair of electrons.
10
Q
What does covalent bonding generally occur between?
A
non-metals
11
Q
What can covalent bonds either be?
A
polar or non-polar
12
Q
What are polar covalent bonds formed between?
A
atoms with different electronegativies
13
Q
What will an atom with the higher electronegativity have?
A
a permanent slightly negative charge
14
Q
What will an atom with the lower electronegativity have?
A
a permanent slightly positive charge
15
Q
What are delta+ and delta- known as?
A
permanent dipoles
16
Q
What non-polar covalent bonds formed between?
A
atoms with the same electronegativities
17
Q
What type of bonds exist as part of the bonding continuum?
A
Pure covalent bonds
Polar covalent bonds
Ionic bonds
18
Q
How is the type of bonding in a compound determined?
A
By the difference in electronegativity between the elements involved
19
Q
What is the type of bonds when the difference in electronegativity is zero?
A
Pure covalent bond.
20
Q
What is the type of bonds when the difference in electronegativity is low?
A
Polar covalent bond
21
Q
What is the type of bonds when the difference in electronegativity is high?
A
Ionic bond
22
Q
What do polar covalent bonds tend to have? e.g. H-F
A
polar covalent structures
23
Q
What do some polar covalent bonds not have?
A
polar covalent structure
24
Q
Give examples of molecules that have polar covalent bonds but don’t have polar covalent structures?
A
carbon dioxide
tetrachloromethane
methane
25
Why do some polar bonds not have polar covalent structures?
Because of the position of the bonds. The bonds are symmetrically opposed and will cancel out
26
What are intermolecular forces?
the attractive forces which hold molecules together i.e. between molecules. The are often also called Van der Waals' forces
27
What are the 3 main types of Van der Waals' forces?
1. London Dispersion Forces
2. Permanent dipole-permanent dipole interactions
3. Hydrogen bonds
28
What are London dispersion forces out of all the intermolecular forces and what do they occur between?
they are the weakest
| occur between all atoms and molecules
29
What are London dispersion forces caused by?
the uneven distribution of electrons which are constantly moving in an atom. This forms a temporary dipole on an atom.
30
What does the uneven distribution of electrons in London dispersion forces form?
This forms a temporary dipole on an atom.
31
What can the atom which has a temporary dipole can do?
induce a dipole in a nearby atom
32
What is a London dispersion force?
an attraction between the temporary dipole and the induced dipole
33
Give two examples of london dispersion forces?
Unreactive noble gases are held together by london dispersion forces and the covalent network layers in graphite are held together by london dispersion forces
34
Describe the trend between the London dispersion forces and the number of electrons in an atom or molecule?
As the number of electrons increases in an atom or molecule, the london dispersion forces also increases
35
When a substance melts or boils, what is broken?
intermolecular forces
36
Describe what happens to the melting/boiling points as we descend down the group of noble gases?
they steadily increase
37
Describe the trend between going down a group and the london dispersion forces?
The number of electrons increases going down the group of noble gases. This means the London dispersion forces are becoming stronger. Due to this. more energy is required to overcome the increasing force of attraction. As a result, the melting/boiling points increases.
38
What are permanent dipole-permanent dipole interactions?
They are intermolecular forces of attraction between polar covalent molecules.
39
When do permanent dipole-permanent dipole interactions occur?
between molecules that have large differences in electronegativity between the atoms of that molecule.
40
What must you note about London dispersion forces and permanent dipole-permanent dipole interactions?
London dispersion forces are still present, however, they are weaker than permanent dipole-permanent dipole interactions
41
What are hydrogen bonds and when do they occur?
a special type of permanent dipole-permanent dipole interactions. They are intermolcular forces of attraction only occur in molecules containing a strongly electronegative element bonds to hydrogen i.e.hydrogen bonded to fluorine, nitrogen, oxygen
42
What must you note as well hydrogen bonds what
| else is present?
london dispersion forces
43
What are hydrogen bonds stronger than?
London dispersion forces and permanent dipole-permanent dipole interactions
44
Why does water, ammonia and hydrogen fluorine have higher boiling points than expected ?
Due to the presence of intermolecular hydrogen bonds
45
Why does ice freeze in an unusual way?
as a result of hydrogen bonding
46
What happens as water is cooled?
it starts to contract but a 4 degrees Celsius it starts to expand (this is why water pipes burst when they freeze).
47
Describe the structure of ice and what effect does this have ?
is an open lattice due to hydrogen bonds. This makes the ice less dense than liquid water and therefore it can float.
48
What are the 2 types of intramolecular bonds ?
polar covalent bonds
| non-polar covalent bonds
49
What is the order of bond strength? (weakest to strongest)
london dispersion forces
permanent dipole-permanent dipole interactions
hydrogen bonds
Ionic, covalent, metallic
50
When melting/boiling most covalent substances what are the only bonds or forces that are broken?
intermolcular forces
51
What structure do metallic and ionic compounds have?
giant lattice
52
What are the 3 other types of structures apart from metallic and ionic lattice?
monatomic
covalent molecular
covalent network
53
What do monatomic structures consist of?
discrete (individual) atoms held together by London dispersion forces
54
What do convalent molecular structures consist of?
discrete (individual) molecules held together by London dispersion forces
55
Give 5 elements that have covalent molecular structures and are also considered diatomic?
```
hydrogen
nitrogen
oxygen
fluorine
chlorine
```
56
Give 2 examples of elements which have covalent molecular structures and are solid at room temperature?
Sulphur
| Phosphorus
57
What structure does sulphur have ?
a covalent molecular structure in which 8 sulphur atoms are covalently bonded to one another. It is a solid at room temperature.
58
What structure does phosphorus have ?
a covalent molecular structure in which 4 phosphorus atoms are covalently bonded to one another. It is a solid at room temperature.
59
What structures do many compounds have and give 4 examples?
covalent molecular structures
| methane, water, ammonia and carbon dioxide
60
What do covalent network structures consist of?
giant lattice of atoms covalently bonded to each other.
61
Give 3 examples of elements with a covalent network structure?
boron
silicon
some types of carbon (diamond and graphite)
62
Why is carbon unique?
it can exist in 3 forms
63
What are the 3 forms of carbon?
fullerenes
carbon diamond
carbon graphite
64
What do fullerenes contain?
contain 60-80 carbon atoms
65
Whate structure do fullerenes have?
covalent molecular structures
66
Do fullerenes conduct electricity?
yes
67
What structure do carbon diamonds have?
covalent network structure
68
What is each carbon atom in the diamond covalently bonded to?
4 other carbon atoms.
69
What is carbon diamond used for and why?
cutting and grinding tools because of its strength
70
What is each carbon atom in graphite covalently bonded to?
to another 3 carbon atoms in a network structure
71
What structure does carbon graphite have?
covalent network structure
72
What can the free electron from each carbon atom do?
move throughout the graphite structure creating delocalised electrons
73
What can the delocalised electrons in carbon graphite move between?
the covalent network layers
74
What does the delocalised electrons make carbon graphite?
a good conductor of electricity
75
Out of the first 20 elements, what elements are monatomic?
Helium
Neon
Argon
76
Out of the first 20 elements, what elements are covalent molecular gas?
```
hydrogen
nitrogen
oxygen
fluorine
chlorine
```
77
Out of the first 20 elements, what elements are covalent molecular soilds?
sulfur
phosphorus
fullerenes ( carbon form)
78
Out of the first 20 elements, what elements are covalent network?
boron
silicon
carbon graphite
carbon diamond
79
Out of the first 20 elements, what elements are metallic?
```
Lithium
Beryllium
Sodium
Magnesium
Aluminium
Potassium
Calcium
```
80
Describe the structure for metallic bonding?
giant lattice of positively charged ions and delocalised electrons
81
Describe the structure for ionic bonding?
giant lattice of oppositely charged ions
82
Describe the structure for monatomic elements?
individual atoms held together by weak intermolecular forces (london dispersion forces)
83
Describe the structure for covalent molecular bonding?
individual molecules held together by weak intermolecular forces (london dispersion forces)
84
Describe the structure for covalent network bonding?
giant lattice of atoms covalently bonded together.
85
What are the 3 properties we look at in terms of bonding and structure?
melting/boiling points
solubility
viscosity
86
What does the melting/boiling points depend on?
the bonds (forces) that must be broken
87
In terms of melting/boiling points what do metallic/ionic compounds generally have and why?
high melting and boiling points due to the large lattice structures that they have.
88
In terms of melting/boiling points what do covalent networks generally have and why?
high melting/boiling points because strong covalent bonds have been broken
89
Give 2 examples of covalent network structure and have very high melting/boiling point ?
silicon dioxide
| silicon carbide
90
In terms of melting/boiling points what do covalent molecular substances depend on ?
the type of intermolecular forces holding the molecules together.
91
What is the order of increasing strength of intermolecular forces and what effect does increasing strength have on the melting/boiling point?
London dipersion forces
permanent dipole - permanent dipole interactions
hydrogen bonds
melting/boiling point increases
92
In terms of melting/boiling points, what would if a substance only has london dispersion forces between the molecules (give example)?
hydrogen gas has a low melting point (-259'c) and boiling point (-253'c).
93
Water has a relatively high melting point for a covalent molecular structure (0'c) and boiling point (100'c), why?
it has stronger hydrogen bonds between its molecules
94
What is another way of saying solubility ?
miscibility
95
What will polar covalent solvents e.g. water, alcohols dissolve?
ionic compounds
| polar covalent compounds
96
What will non-polar covalent solvents e.g. hexane, cyclopentane dissolve?
candle wax
| oil
97
Describe the trend between viscosity of liquids and intermolecular forces?
The viscosity of liquids increases as the inermolecular forces increase.
98
what is the trend between the number of hydrogen bonds in a substance and the viscosity?
as the number of hydrogen bonds increases the viscosity increases
99
What are ionic compounds soluble in?
Water
100
Although most compounds containing metals and nonmetals are ionic what can some actually be ?
Covalent
101
What will a low melting boiling point tell you about the bonding ?
Covalent bonds
102
Give an example of a compound which would appear to be ionic but it actually covalent ?
Titanium chloride
