Bonding & 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 & negative ions

Question 3

Give an example of a iconically 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 & cross diagram

Answer 6

The outer shell

Question 7

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

Answer 7

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

Question 8

Do giant ionic lattices have a high or low melting & boiling point?

Answer 8

They have a 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 positive charge (1+) and oxygen atoms and a negative charge (2-). 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

A 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 2 pairs of electrons?

Answer 15

A double bond

E.g CO2 O = C = O

Question 16

What is formed when atoms share 3 pairs of electrons?

Answer 16

A triple bond

Question 17

What is the 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 suppplied by 1 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 & boiling points?

Answer 23

A small amount of energy is enough to overcome the weak intermolecular forces

Question 24

Can simple molecular structures conduct electricity?

Answer 24

No, they are not conductors

Question 25

Why don’t simple molecular structures conduct electricity?

Answer 25

They 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

Answer 28

High melting & boiling point Non conductors of electricity, (except graphite) Insoluble in polar & 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 & boiling point?

Answer 30

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

Question 31

Draw & describe the structure of a diamond

Answer 31

3D tetrahedral structures of C atoms, with each C atom bonded to 4 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? E.g?

Answer 33

Linear 180 degreees BeCl2

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 degrees

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 degrees

Question 36

What is the shape, diagram and bond angle in a shape with 5 bonded pairs and 0 lone pairs?

Answer 36

Trigonal bipyramid 90 degrees and 120 degrees

Question 37

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

Answer 37

Octahedral 90 degrees

Question 38

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

Answer 38

Pyramidal 107 degrees

Question 39

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

Answer 39

Non linear 104.5 degrees

Question 40

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

Answer 40

2.5 degrees

Question 41

Define electronegativity

Answer 41

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

Question 42

In which direction of the periodic table does electronegativity increase?

Answer 42

Top right, towards fluorine

Question 43

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

Answer 43

The electrons in the bond are evenly distributed

Question 44

What is the most electronegative element?

Answer 44

Fluorine

Question 45

How is a polar bond formed?

Answer 45

Bonding atoms have different electronegativities

Question 46

Why is H2O polar, whereas CO2 is non polar?

Answer 46

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

Question 47

What is meant by intermolecular force?

Answer 47

The attractive force between neighbouring molecules

Question 48

What are the 2 types of intermolecular forces?

Answer 48

Hydrogen bonding Van der Waals’ forces

Question 49

What is the strongest type of intermolecular force?

Answer 49

Hydrogen bonding

Question 50

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

Answer 50

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

Question 51

Describe permanent dipole-induced dipole interactions

Answer 51

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 52

Describe permanent dipole-permanent dipole interactions

Answer 52

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

Question 53

Describe London forces

Answer 53

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

Question 54

Are London forces greater in smaller or larger molecules?

Answer 54

Larger due to more electrons

Question 55

Are London forces greater in smaller or larger molecules?

Answer 55

Larger due to more electrons

Question 56

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

Answer 56

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

Question 57

What condition are needed for hydrogen bond in to occur?

Answer 57

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 forces of attraction between H nucleus and lone pair of electrons on O, N, F

Question 58

Why is ice less dense than liquid water?

Answer 58

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

Question 59

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

Answer 59

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