bonding and structure

Question 1

Why do simple molecular structures have low melting and boiling point

Answer 1

Small amount of energy is enough to overcome the intermolecular forces

Question 2

Describe how metals are malleable and ductile

Answer 2

Layers of positive ions can easily slide over one another and take up different positions

Question 3

In which direction of the periodic table does electronegativity increase

Answer 3

Top right, towards flourine

Question 4

What is the strongest type of intermolecular force

Answer 4

Hydrogen bonding

Question 5

What is meant by intermolecular force

Answer 5

Attractive forces between neighbouring molecules

Question 6

Why is ice less dense than water

Answer 6

• In ice, the water molecules are arranged in an open lattice with hydrogen bonds
• In water, the lattice is collapsed and the molecules are closer together

Question 7

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

Answer 7

• Boiling point increases
• Because the number of electrons increases
• And the strength of london forces also increases

Question 8

How many covalent bonds does oxygen form?

Answer 8

2

Question 9

What are the 3 main types of chemical bonds

Answer 9

1. Ionic
2. Covalent
3. Metallic

Question 10

Why do simple molecular structures not conduct electricity

Answer 10

They have no free charged particles to move around

Question 11

Why do giant covalent structures have high melting and boiling points

Answer 11

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

Question 12

Simple molecular structures dissolve in what type of solvent?

Answer 12

Non polar solvents

Question 13

Describe pernament dipole-dipole interactions

Answer 13

• Some molecules with polar bonds have permanent dipoles
• Leading to forces of attraction between those dipoles and those of neighbouring molecules

Question 14

In what type of solvents do ionic lattices dissolve?

Answer 14

Polar solvents

Question 15

Define electronegativity

Answer 15

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

Question 16

How many covalent bonds does carbon form?

Answer 16

4

Question 17

What is formed when atoms share two pairs of electrons

Answer 17

Double bond

Question 18

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

Answer 18

• In a solid state the ions are in a fixed position and cannot move and carry charge
• When they are in a liquid state the ions are mobile and can freely carry the charge

Question 19

How is a polar bond formed

Answer 19

Bonding atoms have different electronegativities

Question 20

What is the most electronegative element

Answer 20

Flourine

Question 21

Define ionic bonding

Answer 21

The electrostatic attraction between positive and negative ions

Question 22

Can simple molecular structures conduct electricity?

Answer 22

No they are non-conductors

Question 23

What does the shape of a molecule depend on?

Answer 23

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

Question 24

Why is H2O polar, whereas CO2 is non polar

Answer 24

CO2 is a symmetrical molecule so there is no overall dipole

Question 25

What is avarage bond enthalpy?

Answer 25

Measure of average energy needed to break the covalent bond

Question 26

Define metallic bonding

Answer 26

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

Question 27

Describe the bonding in simple molecular structures

Answer 27

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

Question 28

How does graphite conduct electricity

Answer 28

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

Question 29

Give examples of giant covalent structures

Answer 29

1. Diamond 2. Graphite 3. Silicon dioxide

Question 30

What does expansion of the octet mean?

Answer 30

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

Question 31

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

Answer 31

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

Question 32

List properties of giant covalent structures

Answer 32

1. High melting and boiling point 2. Non conductors of electricity, except graphite 3. Insoluble in polar and non-polar solvents

Question 33

Why are ionic compounds soluble in water?

Answer 33

- Water has a polar bond - Hydrogen atoms have a 1+ charge and oxygen atoms have a 2- charge - These charges are able to attract charged ions

Question 34

What does it mean when the bond is non-polar

Answer 34

The electrons in the bond are evenly distributed

Question 35

Describe how metals have high melting and boiling point

Answer 35

Many strong metallic bonds in giant metallic structures so large amounts of heat energy are required to overcome forces and break these bonds

Question 36

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

Answer 36

2.5

Question 37

Describe how metals are good conductors of electricity and heat

Answer 37

There are free electrons that are available to move and carry charge

Question 38

What conditions are needed for hydrogen bonding to occur

Answer 38

- O-H, N-H, F-H bond, lone pair of electrons on O, F, N - O, N, F are highly elecronegative so the H nucleus is exposed - Strong force of attraction between H nucleus and lone pair of electrons on O, N, F

Question 39

What is a lone pair?

Answer 39

Electrons in the outer shell that are not involved in bonding

Question 40

What is a dative covalent bond

Answer 40

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

Question 41

What is formed when atoms share three pairs of electrons?

Answer 41

Triple bond

Question 42

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

Answer 42

Single bond

Question 43

What are the 2 interactions that can be referred as Van Der Waals' forces

Answer 43

- Pernament dipole interaction - Induced dipole interaction

Question 44

Describe London forces

Answer 44

- London forces are caused by **random movements of electrons** - Leading to instantaneous dipoles - **Instantenous dipole** induces a dipole in nearby molecules - Induced dipoles attract one another

Question 45

Are London forces greater in smaller or larger molecules

Answer 45

Larger due to more electrons

Question 46

What are the types of intermolecular forces

Answer 46

1. Hydrogen bonds 2. Pernament dipole-dipole 3. Induced dipole-dipole (London)

Question 47

Do giant ionic lattices have high or low melting and boiling points? Explain your answer

Answer 47

- They have high melting and boiling points - Because a large amount of energy is required to overcome the electrostatic bonds

Question 48

How are oxonium ions formed?

Answer 48

When acid is added to water, H3O+

Question 49

Explain induced dipole-dipole interactions

Answer 49

- When a molecule with a pernament dipole is close to another non-polar molecule it causes the non-polar molecule to become slightly polar leading to attraction

Question 50

Define covalent bonding

Answer 50

The electrostatic attraction between a shared pair of electrons and the nuclei

Question 51

List the types of structures that covalent molecules form

Answer 51

- Simple molecular lattice - Giant covalent lattice

Question 52

Describe the tetrahedral shape

Answer 52

- Angle: 109.5 - Bond pairs: 4 - Lone pairs: 0

Question 53

Describe the linear shape

Answer 53

- Angle: 180 - Bond pairs: 2 - Lone pairs: 0

Question 54

Describe the trigonal bipyramid shape

Answer 54

- Angle: 90 - Bond pairs: 5 - Lone pairs: 0

Question 55

Describe the pyramidal shape

Answer 55

- Angle: 107 - Bond pairs: 3 - Lone pairs: 1

Question 56

Describe the trigonal planar shape

Answer 56

- Angle: 120 - Bond pairs: 3 - Lone pairs: 0

Question 57

Describe the non-linear shape shape

Answer 57

- Angle: 103.4 - Bond pairs: 2 - Lone pairs: 2

Question 58

Describe the octahedral shape

Answer 58

- Angle: 90 - Bond pairs: 6 - Lone pairs: 0