2. Bonding Flashcards

1
Q

How are ions formed?

A

When an atom loses or gains electrons.

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2
Q

What are cations?

A

Positive ions.

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3
Q

What are anions?

A

Negative ions.

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4
Q

What is ionic bonding?

A

The electrostatic attraction between oppositely charged ions. The metal loses electrons and the non-metal gains these electrons.

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5
Q

What is a way of showing ionic bonds?

A

Dot and cross diagram.

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6
Q

What do dot and cross diagrams not show?

A

Don’t show the structure of the compound, the siz of the ions or how they are arranged.

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7
Q

What is a giant ionic lattice?

A

Ionic compound, regular lattice arrangement, very strong electrostatic forces of attraction between oppositely charged ions, in all directions.

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8
Q

What are adavantages and disadvantages of the ball and stick model?

A

+ Shows the regular pattern of the compounds and shows how the ions are arranged.
- Model isn’t to scale, relative sizes of ions not shown, there are no gaps between ions.

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9
Q

What are properties of ionic compounds?

A
  1. High melting points and boiling points due to the strong bonds between the ions. Takes a lot of energy to overcome this attraction.
  2. Can’t conduct electricity when solid. When melted the ions are free to move so can carry an electrical current.
  3. Carry an electric current when dissolved in water as the ions will be free to move.
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10
Q

What is covalent bonding?

A

The electrostatic attraction of non-metal atoms between the positively charged nuclei and their shared pair of electrons.

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11
Q

What are ways of representing covalent bonds?

A

Dot and cross diagrams, displayed formula and 3D model.

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12
Q

What is an advantage and disadvantage of the dot and ross model to show a covalent bond?

A

+ Show which atoms the electrons in a covalent bond come from.
- Don’t show relative sizes of the atoms, or how they are arranged in space.

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13
Q

What is an advantage and disadvantage of using the displayed formula to show a covalent bond?

A

+ Show how atoms are connected in large molecules.

- Don’t show the 3D structure or which atoms the electrons in the covalent bond have come from.

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14
Q

What is a diadvantage of using the 3D model to show covalent bonds?

A

They don’t show where electrons in the bond have come from.

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15
Q

Give example of simple molecular substances.

A

Hydrogen, chlorine, oxygen, nitrogen, methane, water, hydrogen chloride.

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16
Q

What are the properties of simple molecular substances?

A

Molecules held together by very strong covalent bonds but the forces of attraction between the molecules are very weak.

  1. Have low boiling points: to melt or boil simple molecular compounds, you only need to break the feeble intermolecular forces and not the covalent bonds.
  2. Gases or liquids are room temperature.
  3. Melting and boiling points increase as the molecules get bigger: As they get bigger the strength of the intermolecular forces increases so more energy is needed to break them.
  4. Don’t conduct electricity as they aren’t charged, no free electrons or ions.
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17
Q

What is a polymer?

A

Small units linked together to form a long molecule with repeating sections.

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18
Q

Why are most polymers solid at room temperature?

A

Intermolecular forces are larger than between simple molecular molecules so more energy is needed to break them.

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19
Q

Why do most polymers have lower boiling points than giant molecular compounds or ionic compounds?

A

Their intermolecular forces are still weaker than ionic or covalent bonds.

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20
Q

What are the properties of giant covalent structures?

A
  1. Very high melting points and boiling points. Lots of energy is needed to break the covalent bonds between atoms.
  2. Don’t conduct electricity, as they don’t contain charged particles (not even when molten), except for graphite.
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21
Q

Why is diamond really hard?

A

Each carbon atom forms four covalent bonds.

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22
Q

Why does diamond have a very high melting point?

A

Each carbon atom forms four strong covalent bonds. These take a lot of energy to break.

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23
Q

Why doesn’t diamond conduct electricity?

A

Has no free electrons.

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24
Q

How are the carbon atoms arranged in graphite?

A

Each carbon atom forms three covalent bonds creating sheets of carbon atoms arranged in hexagons.

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25
Q

Why is graphite soft and slippery?

A

There aren’t any covalent bonds between the layers, they are only held together weakly, so are free to move over each other.

26
Q

Why does graphite have a high melting point?

A

The covalent bonds in the layers take a lot of energy to break.

27
Q

Why does graphite conduct electricity and thermal energy?

A

Only forms three bonds so each carbon atom has a delocalised electron that is free to move.

28
Q

What is graphene?

A

One sheet of carbon atoms joined together in hexagons. The sheet is just one atom thick, making it a two dimentional compound.

29
Q

Why is graphene strong?

A

It has a network of covalent bonds.

30
Q

Why is it useful that graphene is light?

A

It can be added to composite materials to improve their strength without adding much weight.

31
Q

Why can graphene be used in electronics?

A

Contains delocalised electrons so can conduct electricity through the whole structure.

32
Q

What are fullerenes?

A

Molecules of carbon shaped like close tubes or hollow balls. Mainly made up of carbon atoms shaped in hexagons but also pentagons and heptagons.

33
Q

What is a use of fullerenes?

A

Can be used to ‘cage’ other molecules. Can be used to deliver drugs into the body. Can also make good lubricants.

34
Q

Why can fullerenes help make good industrial catalysts?

A

Have a large surface area so individual catalyst molecules can be attached to the fullerene.

35
Q

What are nanotubes?

A

Tiny carbon cylinders formed by fullerenes.

36
Q

What are features of nanotubes?

A

Have a high ratio between length and diameter. Conduct both electricity and heat. Have high tensile strength (don’t break when streched).

37
Q

What is nano technology?

A

Technology that uses very small particles.

38
Q

What can nanotubes be used in?

A

Electronics or to strengthen materials without adding much weight, such as tennis racket frames.

39
Q

What is metallic bonding?

A

The electrostatic attraction between positive metal ions and their negative electrons.

40
Q

What part of metallic bonds produce all the properties of the metal?

A

The delocalised electrons.

41
Q

Why are metals generally solid at room temperature?

A

The electrostatic forces between the metal atoms and the delocalised electrons are very strong so need lots of energy to be broken. This means that they have high melting and boiling points.

42
Q

What are the properties of metals?

A

Solid at room temperature, good conductors of electricity and heat, malleable.

43
Q

Why are metals good conductors of electricity and heat?

A

The delocalised electrons carry electrical current and thermal energy through the whole structure.

44
Q

Why are most metals malleable?

A

Layers of atoms in the metal can slide over each other meaning they can be bent, hammered or rolled into flat sheets.

45
Q

What are alloys?

A

A mixture of two or more metals or a metal and another element.

46
Q

Why are alloys harder than pure metals?

A

Different elements have different sized atoms. So when a new element is mixed in with a pure metal, the new metal will distort the layers of metal atoms making it more diffucult for them to slide over each other.

47
Q

What are the three states of matter?

A

Solid, liquid and gas.

48
Q

What does what state something is at a certain temperature depend on?

A

How strong the forces of attraction are between the particles of material.

49
Q

How strong the forces of attraction between particles depends on what?

A
  1. The material (structure/ type of bonding).
  2. The temperature.
  3. The pressure.
50
Q

What does the particle theory explain?

A

How the particles in a material behave in each of the three states by considering each particle as small, solid, inelastic spheres.

51
Q

Describe solids.

A
  1. Strong forces of attraction between particles which holds them close together in fixed positions to form a very regular lattice arrangement.
  2. The particles don’t move from their positions, so all solids keep a definite shape and volume.
  3. Particles vibrate about their positions. The hotter the solid becomes, the more they vibrate causing solids to expand slightly when heated.
52
Q

Describe liquids.

A
  1. There’s weak forces of attraction between the particles. They are randomly arranged and free to move past each other, but tend to stick closely together.
  2. Have a definite volume but don’t keep a definite shape, will flow to fill the bottom of a container.
  3. Particles are constantly moving with random motion. The hotter the liquid gets, the faster they move, causing liquids to expand slightly when heated.
53
Q

Describe gases.

A
  1. Very weak forces of attraction. Free to move and far apart. Particles in gases travel in straight lines.
  2. Don’t keep a definite shape or volume and will always fill any container.
  3. Particles constantly move in a random motion. The hotter the gas gets, the faster they move. Either expand when heated or the pressure increases.
54
Q

What are some disadvantages of the particle theory model?

A

In reality, the particles aren’t solid or inelastic and they aren’t spheres. Also the model doesn’t show the forces between the particles so there is no way of knowing how strong they are.

55
Q

Page 37

A

Revise it ehhe.

56
Q

What are coarse particles?

A

Diameter between 2500nm and 10000nm. Dust.

57
Q

What is the diameter of fine particles?

A

Between 100nm and 2500nm.

58
Q

What is the diameter of nanoparticles?

A

Between 1nm and 100nm.

59
Q

How do you find the surface area to volume ratio?

A

Surface area/ volume.

60
Q

What are some uses of nanoparticles?

A
  1. Catalysts - huge SA to volume ratio.
  2. Deliver drugs - nanomedicine, fullerenes absorbed easily.
  3. Computer chips - conduct electricity so can be used in tiny electric circuits.
  4. Added to polymer fibres that can be used in surgical masks, wound dressing and also deodrants - silver nanoparticles have anitbacterial properties.
  5. Cosmetics - can improve mosturisers without making them oily.
61
Q

Why are some people against the use of nanoparticles?

A

They way they affect the body isn’t fully understood. We don’t know the long term health impacts - should be clearly labeled.

62
Q

Why are nanoparticles used in sun creams and what is bad about that?

A

Have been shown to be better at protecting skin from harmful UV rays. Also give better skin coverage. Not yet clear whether they can get into your body and damage cells. It is also possible that they could be washed away and damage the environment.