C3 : Structure and Bonding

Question 1

Why are ionic compounds crystals?

Answer 1

Due to their regular structure of the ionic lattice.
- the ions are joined by strong ionic bonds between oppositely charged ions

Question 2

Why do ionic compounds have high melting/boiling points?

Answer 2

A lot of energy is needed to break the bonds bc they’re very STRONG.

Question 3

Why can a solid ionic substance NOT conduct electricity but a molten/aqueous ionic substance can? (6)

Answer 3

• When solid, ions are bonded together by the lattice in a fixed position .
• ions cant move to carry the electrical charge
• in liquid, ions can break free from lattice
• able to move, bc supplied with enough energy to become a liquid
• can carry electrical charge

Question 4

What do ionic bonds form between?

Answer 4

Metal / non-metal - conduct in molten/aqueous state

Question 5

What do covalent bonds form between?

Answer 5

2 non- metals
- don’t conduct electricity/heat

Question 6

Why do the simple covalent bonds have low MP/BP?

Answer 6

Bc intermolecular forces are relatively weak - less energy is needed to OVERCOME the forces
Intermolecular forces are weaker than covalent bonds - covalent bonds aren’t broken

Question 7

compare the strength of bonds between atoms in the molecule to the forces that exist between the different molecules. (2)

Answer 7

The strength of the coaled bonds are stronger Tham the intermolecular forces - they are weak.

Question 8

Examples of SIMPLE covalent bonds. (3)

Answer 8

H20 - water
CO2 - carbon dioxide
NH3 - ammonia

Question 9

Examples of giant covalent bonds. (5)

Answer 9

Diamond
graphite
graphene
fullerenes
silicon dioxide

Question 10

Why do giant covalent bonds have high MP/BP?

Answer 10

• Bc they don’t form molecules
  -A lot of energy is needed to break the strong covalent bonds

Question 11

What are graphite’s properties and why do they have these properties? (3)

Answer 11

Soft/slippery - layers are far apart
- forces between layers are weak
- easy to separate layers /slide

High MP
- difficult to break strong covalent bonds

Conducts Electricity/Heat
- 3 of the 4 outer electrons are held in place in the layer
- the 4th electron is is DELOCALISED. Electron current can be carried/travel through material.

Question 12

What are allotropes?

Answer 12

Different structural forms of the same element in the same physical state.

Question 13

what are the allotropes of carbon?

Answer 13

Diamond
Graphite
Graphene
Fullerenes

Question 14

Why do metals have high BP/MP?

Answer 14

• takes a lot of energy to separate metal ions from fixed positions, as electrostatic forces are very strong

Question 15

How are ions held together in a metal? (3)

Answer 15

• lattice structure of positive ions
• with delocalised electrons/free electrons
  -Strong electrostatic forces between the electrons and + ions bond the metal ions together.

Question 16

How does the structure and bonding in metals allow them to bent and shaped?

Answer 16

• layers of atoms are able to SLIDE easily over each other

Question 17

Properties of diamond and uses.

Answer 17

• very hard - lots of covalent bonds
  - takes a lot of energy to break these bonds
  - giant lattice structure
• BAD conductor of ELECTRICITY
  - no delocalise electrons

USED FOR : jewellery
cutting tools/blade edges

Question 18

Properties of graphene. SFC

Answer 18

STRONG - due to strong covalent bonds/unbroken pattern
CONDUCTS ELECTRICITY/HEAT - has free electrons to carry current/heat
3/4 electrons are bonded , 4th Is delocalised
FLEXIBLE - bonds between atoms are flexible

Question 19

What can fullerenes be used for and what properties allow this?

Answer 19

-can CAGE other molecules - good for DRUG DELIVERY
- large SURFACE AREA - make them good industrial catalysts
WEAK intermolecular forces , so SLIPPERY/LOW MP - lubricants

Question 20

describe the nature of chemical bonding in ionic strictures? (3)

Answer 20

• giant lattice structure
  -held together by strong electrostatic forces between oppositely charged ions
  -theses forces act in all directions

Question 21

why are alloys harder than pure metals?

Answer 21

• atoms/ions/particles are different sizes
• layers can’t slide over eachother

Question 22

NANOPARTICLES SIZE?

Answer 22

(1X10-9) - (1X10-7)
1nm - 100nm

Question 23

surface area: volume ration equyation?

Answer 23

SA / VOL

Question 24

USES OF nanoparticles ?

Answer 24

• high SA:V - CATALYSTS
  DRUG DELIVERY - absorbed into body easily
  ELECTRIC CIRCUITS - conductor
  POLYMER FIBRES - (surgical masks/wound dressing) - ANTIBACTERIAL
  COSMETICS

Question 25

what are effects on health by using nanoparticles?

Answer 25

• jnot sure LONG TERM EFFECTS
• SHld be clearly labelled so consumer can decide whether to use product or not
• could DAMAGE CELLS/DAMAGE ENVIRON

Question 26

how are nanoparticles able to catalyse reaction?

Answer 26

• A catalyst provides an alternative reaction pathway with lower activation energy
• Often by creating more surface area for reactant particles to collide
• As nanoparticles have a high surface area to volume ratio
• They provide much more surface area for catalytic activity to occur
• Hence increasing the rate of reaction