2.2.2 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 an ionically bonded lattice

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

Answer 7

In solid state the ions are held 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 points? 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

Question 10

Why are ionic compounds soluble in water?

Answer 10

Water has a polar bond. Hydrogen atoms have a δ⁺ charge and oxygen atoms have a δ⁻ 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 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 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 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 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

They have no free charged particle to mave around

Question 26

Simple molecular structures dissolve in what type of solvent?

Answer 26

Non polar solvents

Question 27

Give an example of a giant covalent structure

Answer 27

- Diamond - Graphite - Silicon dioxide

Question 28

What are some properties of giant covalent structures?

Answer 28

- High melting and boiling points - Non conductors of electricity except graphite - Insoluble in polar and non polar solvents

Question 29

How does graphite conduct electricty?

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 points?

Answer 30

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

Question 31

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 and bond angle in a shape with 2 bonded pairs and 0 lone pairs

Answer 33

Linear | 180°

Question 34

What is the shape and bond angle in a shape with 3 bonded pairs and 0 lone pairs

Answer 34

Trigonal planar | 120°

Question 35

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

Answer 36

Trigonal bipyramidal | 90° and 120°

Question 37

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

Answer 37

Octahedral | 90°

Question 38

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

Answer 38

Pyramidal | 107°

Question 39

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

Answer 39

Non linear | 104.5°

Question 40

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

Answer 40

2.5°

Question 41

Define electronegativity

Answer 41

The abilty 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 is meant 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 symetrical molecule so there is no overall dipole

Question 47

What is meant by intermolecular force

Answer 47

Attractive forces between neighbouring molecules

Question 48

What are the two 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

Describe London forces?

Answer 50

- Londone 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 51

Are London forces greater in smaller or larger molecules?

Answer 51

Larger due to more electrons

Question 52

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

Answer 52

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

Question 53

What conditions are needed for hydrogen bonding to occur?

Answer 53

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 54

Why is ice less dense than liquid water?

Answer 54

- In ice the water molecules are arranged in orderly patterns. It has an open lattice with hydrogen bonds - In water the lattice is collapsed and the molecules are closer toegether

Question 55

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

Answer 55

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