2:Bonding and Structure

Question 1

What is ionic bonding?

Answer 1

The electrostatic attraction between oppositely charged ions

Question 2

What is the formula for hydroxide ion?

Answer 2

OH−

Question 3

What is the formula for nitrate ion?

Answer 3

NO3^-

Question 4

What is the formula for ammonium ion?

Answer 4

NH4 ^+

Question 5

What is the formula for sulphate ion?

Answer 5

SO4^2-

Question 6

What is the formula for carbonate ion?

Answer 6

CO3^2-

Question 7

What are the features of giant ionic structures?

Answer 7

• regular structure
• cubic shape
• giant repeating patterns

Question 8

Give an example of a giant ionic structure?

Answer 8

NaCl

Question 9

Why can ionic compounds dissolve in water?

Answer 9

Water molecules are polar, so they attract the anions and cation which break up the structure

Question 10

Why can ionic structures conduct electricity when molten or dissolved in a solution?

Answer 10

The ions are free to move around.

Question 11

Why do ionic compounds have high melting points?

Answer 11

There are many strong electrostatic forces between oppositely charged ions
- therefore more energy is needed to overcome these forces

Question 12

Why are ionic compounds brittle?

Answer 12

When struck with a hammer the layers slide - so the cations align with cations and anions align with anions. They repel each other and the structure breaks apart

Question 13

Why does the size of the charge increase the strength of the ionic bond?

Answer 13

The bigger the charge of the ion the stronger the electrostatic attraction between ions.
- Therefore more energy is required to overcome these forces

Question 14

Why does the size of the ion (ionic radius) affect the strength of the ionic bond?

Answer 14

The smaller the ion the stronger the electrostatic attraction between the ions
-> smaller ions can pack together more closely so more energy is required to overcome these strong forces

Question 15

Which ions have the highest charge density?

Answer 15

Ions with smaller radius and higher charge

Question 16

Why does ionic radius increase as you go down a group?

Answer 16

Number of electrons shell increases

Question 17

Why does the ionic radius in isoelectric ions decrease as atomic number increases?

Answer 17

More protons for the same number of electrons so attractive force from nucleus increases

Question 18

Describe the experiment to show evidence for charged particles?

Answer 18

Electrolysis of copper(II)chromate(VI) on wet filter paper

• add a drop of green copper(II)chromate(VI) is placed on wet filter paper and electricity is passed through (to separate the ions)
• Positive Blue Cu2+ ions move to cathode
• Negative Yellow CrO4^2- ions move to anode

Question 19

What is covalent bonding?

Answer 19

The electrostatic attraction between a shared pair of electrons of two non-metal atoms and their nuclei

Question 20

What are dative bonds (co-ordinate bonds)?

Answer 20

Covalent bond where the shared pair of electrons comes from one atom

Question 21

What happens to bond enthalpy the shorter the bond?

Answer 21

The bond enthalpy will be higher

Question 22

What two forces are acting in a covalent bond?

Answer 22

• attraction - between shared pair of electrons and positive nuclei
• repulsion - between like charged electrons and like charged nuclei

Question 23

What is bond length a result of?

Answer 23

The balance between the attraction and repulsion force in a covalent bond.

Question 24

How does a greater electron density cause high bond enthalpy?

Answer 24

There is a stronger attraction force so atoms are pulled closer towards each other. This leads to shorter bond length which results in higher bond enthalpy.

Question 25

Why does the C-C triple bond have a higher bond enthalpy than a C-C single bond?

Answer 25

C-C triple bond has a higher electron density shared, so there is a shorter bond * - so there is a higher bond enthalpy*

Question 26

Why do molecules have specific shapes?

Answer 26

- Bonds repel each other equally as they contain electrons so they will want to be as far apart as possible

Question 27

What is the shape of a molecule with 2 bond pairs and 0 lone pairs?

Answer 27

Linear

Question 28

What is the shape of a molecule with 3 bond pairs and 0 lone pairs?

Answer 28

Trigonal planar

Question 29

What is the shape of a molecule with 4 bond pairs and 0 lone pairs?

Answer 29

Tetrahedral

Question 30

What is the shape of a molecule with 5 bond pairs and 0 lone pairs?

Answer 30

Trigonal Bipyramidal

Question 31

What is the shape of a molecule with 6 bond pairs and 0 lone pairs?

Answer 31

Octahedral

Question 32

What is the shape of a molecule with 3 bond pairs and 1 lone pairs?

Answer 32

Trigonal pyramidal

Question 33

What is the shape of a molecule with 2 bond pairs and 2 lone pairs?

Answer 33

V-shaped

Question 34

What are the properties of graphite?

Answer 34

1) each carbon has 3 bonds with one delocalised electron 2) conduct electricity and thermal energy 3) layers slide over each other 4) lightweight 5) insoluble

Question 35

Why can graphite transfer thermal energy and conduct electricity?

Answer 35

Delocalised electrons

Question 36

Why can the layers of graphite slide over each other?

Answer 36

There are weak forces between the layers

Question 37

Why is graphite lightweight?

Answer 37

Layers are far apart compared to its covalent bond length. This means it has a low density and therefore lightweight

Question 38

Why is graphite insoluble?

Answer 38

Covalent bonds are too strong to break

Question 39

What are the properties of diamond?

Answer 39

1) each carbon atoms has 4 bonds 2) can conduct heat well 3) very high melting point 4) doesn’t conduct electricity 5) insoluble 6) same structure as SiO2

Question 40

Why can diamond conduct heat well?

Answer 40

It’s tightly packed, in a rigid arrangement

Question 41

Why can’t diamond conduct electricity but graphite and grapheme can?

Answer 41

Diamond doesn’t have any delocalised electrons to conduct or transfer energy

Question 42

Why is diamond insoluble?

Answer 42

Covalent bonds are too strong to break

Question 43

What are the properties of graphene?

Answer 43

1) it is a single layer of graphite *(so it’s 1 atom thick)* 2) made up of hexagonal carbon rings 3) lightweight and transparent 4) contains delocalised electrons which strengthen the covalent bonds

Question 44

Why is graphene lightweight and transparent?

Answer 44

Because it’s one atom thick

Question 45

What is metallic bonding?

Answer 45

The strong electrostatic attraction between the nuclei of metal cations and delocalised electrons

Question 46

What increases the melting point in metallic bonding?

Answer 46

More electrons being donated to the sea of delocalised electrons

Question 47

Why do metal compounds have a high melting point?

Answer 47

Due to strong electrostatic attraction between cations and delocalised electrons which require a high amount of energy to overcome

Question 48

Why are metal compounds insoluble?

Answer 48

Due to strong metallic bonds

Question 49

Why are metal compounds malleable and ductile?

Answer 49

Ion layers can slide across each other and still retain an attraction between cations and delocalised electrons

Question 50

What is electronegativity?

Answer 50

The ability for an atom to attract a pair of electrons towards itself in a covalent bond

Question 51

What is the most electronegative element, according to the Pauling Scale?

Answer 51

Fluorine

Question 52

What scale do we use to determine electronegativity?

Answer 52

The Pauling Scale

Question 53

What does a bigger difference in electronegativity between atoms mean?

Answer 53

The more ionic the compound will be

Question 54

What does it mean if a bond is polar?

Answer 54

There is a significant difference in electronegativity between atoms *- the bigger the difference in electronegativity the more polar the bond will be*

Question 55

What makes a covalent bond non-polar?

Answer 55

When atoms have the same/similar levels of electronegativity. - *e.g. hydrocarbons are non-polar*

Question 56

Order the intermolecular forces from strongest to weakest (1 being the strongest).

Answer 56

1) Hydrogen bonds 2) Permanent dipole - dipole 3) London forces

Question 57

When does hydrogen bonding occur?

Answer 57

When hydrogen on one molecule forms a bond with the lone pair of either **oxygen**,**fluorine** or **nitrogen**

Question 58

What is permanent dipole-dipole ?

Answer 58

The δ- of one permanent dipole molecule is attracted to the δ+ of another

Question 59

What are London forces?

Answer 59

Forces that occur when the δ+ of a temporary dipole molecule is attracted to the δ- of another

Question 60

What is the difference between bonds and forces?

Answer 60

Forces occur between molecules Bonds occur between atoms