Module 2 - Bonding and Structure

Question 1

What are the 3 main types of
chemical bonds?

Answer 1

● Ionic
● Covalent
● Metallic

Question 2

Define ionic bonding

Answer 2

The electrostatic attraction between
positive and negative ions

Question 3

Give an example of a ionically
bonded substance

Answer 3

NaCl (Sodium Chloride - salt)

Question 4

Define covalent bonding

Answer 4

Electrostatic attraction between a shared
pair of electrons and the nuclei

Question 5

Define metallic bonding

Answer 5

Electrostatic attraction between the
positive metal ions and the sea of
delocalised electrons

Question 6

Electrons in which shell are
represented in a dot and cross
diagram?

Answer 6

The outer shell

Question 7

Why does giant ionic lattices
conduct electricity when liquid
but not when solid?

Answer 7

In solid state the ions are in fixed
positions and thus cannot move. When
they are in liquid state the ions are
mobile and thus can freely carry the
charge

Question 8

Giant ionic lattices have high
or low melting and boiling
point? Explain your answer

Answer 8

They have high melting and boiling point
because a large amount of energy is
required to overcome the electrostatic
bonds

Question 9

In what type of solvents do
ionic lattices dissolve?

Answer 9

Polar solvents
E.g water

Question 10

Why are ionic compounds
soluble in water?

Answer 10

Water has a polar bond. Hydrogen atoms
have a delta + charge and oxygen atoms
have a delta - charge. These charges are
able to attract charged ions

Question 11

What is it called when atoms
are bonded by a single pair of
shared electrons?

Answer 11

Single bond

Question 12

How many covalent bonds
does carbon form?

Answer 12

4

Question 13

How many covalent bonds
does oxygen form?

Answer 13

2

Question 14

What is a lone pair?

Answer 14

Electrons in the outer shell that are not
involved in the bonding

Question 15

What is formed when atoms
share two pairs of electrons?

Answer 15

Double bond

Question 16

What is formed when atoms
share three pairs of electrons?

Answer 16

Triple bond

Question 17

What is average bond
enthalpy?

Answer 17

Measure of average energy needed to
break the bond

Question 18

What is a dative covalent
bond?

Answer 18

A bond where both of the shared
electrons are supplied by one atom

Question 19

How are oxonium ions
formed?

Answer 19

Formed when acid is added to water,
H3O+

Question 20

What does expansion of the
octet mean?

Answer 20

When a bonded atom has more than 8
electrons in the outer shell

Question 21

What are the types of covalent
structure?

Answer 21

● Simple molecular lattice
● Giant covalent lattice

Question 22

Describe the bonding in simple
molecular structures

Answer 22

Atoms within the same molecule are held
by strong covalent bonds and different
molecules are held by weak
intermolecular forces

Question 23

Why do simple molecular
structures have low melting
and boiling point?

Answer 23

Small amount of energy is enough to
overcome the intermolecular forces

Question 24

Can simple molecular
structures conduct electricity?

Answer 24

No, they are non conductors.

Question 25

Why do simple molecular structures not conduct electricity?

Answer 25

The have no free charged particles to move around

Question 26

Simple molecular structures dissolve in what type of solvent?

Answer 26

Non polar solvents

Question 27

Give examples of giant covalent structures

Answer 27

● Diamond ● Graphite ● Silicon dioxide, SiO2

Question 28

List some properties of giant covalent structures? (3)

Answer 28

● High melting and boiling point ● Non conductors of electricity, except graphite ● Insoluble in polar and non polar solvents

Question 29

How does graphite conduct electricity?

Answer 29

Delocalised electrons present between the layers are able to move freely carrying the charge

Question 30

Why do giant covalent structures have high melting and boiling point?

Answer 30

Strong covalent bonds within the molecules need to be broken which requires a lot of energy

Question 31

Draw and describe the structure of a diamond

Answer 31

3D tetrahedral structure of C atoms, with each C atom bonded to four others

Question 32

What does the shape of a molecule depend on?

Answer 32

Number of electron pairs in the outer shell Number of these electrons which are bonded and lone pairs

Question 33

What is the shape, diagram and bond angle in a shape with 2 bonded pairs and 0 lone pairs?

Answer 33

Linear 180°

Question 34

What is the shape, diagram and bond angle in a shape with 3 bonding pairs and 0 lone pairs?

Answer 34

Trigonal planar 120°

Question 35

What is the shape, diagram and bond angle in a shape with 4 bonded pairs and 0 lone pairs?

Answer 35

Tetrahedral 109.5°

Question 36

What is the shape,diagram and bond angle in a shape with 6 bonded pairs and 0 lone pairs?

Answer 36

Octahedral 90°

Question 37

What is the shape, diagram and bond angle in a shape with 3 bonded pairs and 1 lone pairs?

Answer 37

Pyramidal 107°

Question 38

What is the shape, diagram and bond angle in a shape with 2 bonded pairs and 2 lone pairs?

Answer 38

Non linear 104.5°

Question 39

By how many degrees does each lone pair reduce the bond angle?

Answer 39

2.5°

Question 40

Define electronegativity

Answer 40

The ability of an atom to attract the pair of electrons (the electron density) in a covalent bond

Question 41

In which direction of the periodic table does electronegativity increase?

Answer 41

Top right, towards fluorine

Question 42

What does it mean when the bond is non-polar?

Answer 42

The electrons in the bond are evenly distributed

Question 43

What is the most electronegative element?

Answer 43

Fluorine

Question 44

How is a polar bond formed?

Answer 44

Bonding atoms have different electronegativities

Question 45

Why is H2O polar, whereas CO2 is non polar?

Answer 45

CO2 is a symmetrical molecule, so there is no overall dipole

Question 46

What is meant by intermolecular force?

Answer 46

Attractive force between neighbouring molecules

Question 47

What are the 2 types of intermolecular forces?

Answer 47

● Hydrogen bonding ● dipole dipole ● dispersion

Question 48

What is the strongest type of intermolecular force?

Answer 48

Hydrogen bonding

Question 49

What are the 2 interactions that can be referred as Van der Waals’ forces?

Answer 49

● Permanent dipole - induced dipole interaction ● Permanent dipole - permanent dipole interaction

Question 50

Describe permanent dipole-induced dipole interactions

Answer 50

● When a molecule with a permanent dipole is close to other non polar molecules it causes the non polar molecule to become slightly polar leading to attraction

Question 50

Describe permanent dipolepermanent dipole interactions

Answer 50

Some molecules with polar bonds have permanent dipoles → forces of attraction between those dipoles and those of neighbouring molecules

Question 51

Describe London forces

Answer 51

● induced dipole-induced dipole attraction ● London forces are caused by random movements of electrons ● This leads to instantaneous dipoles ● Instantaneous dipole induces a dipole in nearby molecules ● Induced dipoles attract one another

Question 52

Are London forces greater in smaller or larger molecules?

Answer 52

Larger due to more electrons

Question 53

Does boiling point increase or decrease down the noble gas group? Why?

Answer 53

Boiling point increases because the number of electrons increases and hence the strength of London forces also increases

Question 54

What conditions are needed for hydrogen bonding to occur?

Answer 54

* O-H, N-H or F-H bond, lone pair of electrons on O, F, N * Because O, N and F are highly electronegative, H nucleus is left exposed * Strong force of attraction between H nucleus and lone pair of electrons on O, N, F

Question 55

Draw a diagram of hydrogen bonding

Question 56

Why is ice less dense than liquid water?

Answer 56

● In ice, the water molecules are arranged in a orderly pattern. It has an open lattice with hydrogen bonds. ● In water, the lattice is collapsed and the molecules are closer together.

Question 57

Why does water have a melting/ boiling point higher than expected?

Answer 57

Hydrogen bonds are stronger than other intermolecular forces so extra strength is required to overcome the forces