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Chemistry > Topic 2: Structure and Bonding > Flashcards

Topic 2: Structure and Bonding Flashcards

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1
Q

What is a bond?

A

Bonds are forces if attraction that hold atoms together.

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2
Q

Why are bonds formed between atoms?

A

To make them more stable. When bonds form between energy is released from the atoms making them more stable and less reactive.

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3
Q

What are the most stable gases and why?

A

Noble gases because they have a full outer shell of electrons so are inert/unreactive.

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4
Q

What is an ion?

A

An atom with a charge.

An atoms or group of atoms with an electrical charge due to the gain or loss of electrons.

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5
Q

What are cations?

A

Atoms that lose electrons and form a positive charge as they then have more protons than electrons. E.g metals.

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6
Q

What are anions?

A

Atoms that gain electrons that form a positive charge. E.g non-metals. The have more electrons than protons so form a negative charge.

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7
Q

What are electrostatic forces?

A

Forces of attraction between all positively and negatively charged objects. These forces hold the oppositely charged ions together and form an ionic bond between them.

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8
Q

Ionic bonds are formed between….

A

A metal and a non-metal.

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9
Q

Covalent bonds are formed between…

A

Non-metal and a non-metal.

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10
Q

Metallic binds are formed between…

A

Metal and a metal.

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11
Q

What does the ion formed in an ionic bind depend on?

A

The elements position in the periodic table and the number of electrons in its outer shell.

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12
Q

What is an ionic compound and how is it formed?

A

They are formed by the loss and gain of electrons. They are held together by strong electrostatic forces of attraction between oppositely charged ions. The strong ionic bonds allow ‘billions’ of ions to be packed together in a repeating arrangement forming an ionic lattice structure.

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13
Q

What bonds are formed between an ionic compound?

A

Electrostatic bonds. Ionic bonds.

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14
Q

What is an ionic bond?

A

A strong electrostatic force of attraction between oppositely charged ions.

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15
Q

What is an ionic compound?

A

A substance made up of ions of different elements.

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16
Q

What do ionic compounds often form in a solid state?

A

They often form crystals when solid because of their irregular lattice structure. Crystals are pieces of solid that have a particular regular shape, flat surfaces and sharp edges.

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17
Q

What charge do ionic compounds have?

A

Ionic compounds are electrically neutral (they have no overall charge).

So the formula of an ionic compound contains the same number of positive charges as negative charges.

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18
Q

What is a polyatomic ion?

A

A group of atoms that have a positive charge or a negative charge due to the loss or gain of electrons.

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19
Q

What are the polyatomic ions?

A

Ammonium
Nitrate
Hydroxide

Carbonate
Sulphate
Sulphide

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20
Q

Why must some polyatomic ions be written in brackets?

A

If an ionic formula contains 2 or more of the same polyatomic ions then the formula of the polyatomic ion must be written inside of brackets.

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21
Q

What do all ionic compounds contain?

A

Charged particles called ions.

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22
Q

How does an ionic bond form?

A

Between a metal and non metal. The oppositely charged ions in an ionic compound are held together by strong electrostatic forces of attraction, which are called ionic bonds.

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23
Q

Why do ionic bonds have strong melting/boiling points?

A

The electrostatic force of attraction between oppositely charged ions are very strong. A lot of energy is needed to overcome these forces in order to separate the ions and cause the substances to melt. This is why they have high melting and boiling points in order to over come these forces.

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24
Q

Do ionic compounds conduct electricity?

A

Ionic compounds do conduct electricity when molten or dissolved because when in this state they have free flowing ions to carry charge. They do not conduct electricity when in a solid state.

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25
Q

Two conditions must be met for a substance to conduct electricity:

A
  • it must contain charged particles.

- these particles must be free to move.

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26
Q

What enables an ionic compound to carry electricity?

A

When an ionic compound conducts electricity, it is the charges ions that carry the current. (Not only electrons).

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27
Q

Why do ionic compounds not conduct electricity when in a solid state?

A

They do not conduct electricity in a solid state because the ions are not free to move from place to place.

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28
Q

Why can ionic compounds carry electricity/ current when molten or dissolved?

A

When the ionic compound is molten or in aqueous solution, the ions are free to move and therefore free to carry current. Most ionic compounds are soluble in water and form an aqueous solution.

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29
Q

What are negative ions known as?

A

They are known as anions and they are attracted to to the positive electrode called an anode.

30
Q

What are positive ions known as?

A

The positive ions are known as cations and they are attracted to the negative electrode known as the cathode.

31
Q

Is it the electrons that carry the electronic charge in ionic compounds?

A

No, it is the ions moving that enable ionic compounds to conduct electricity not the electrons moving.

32
Q

What is a covalent bond?

A

A bond formed when a pair of electrons is shared between two atoms.

33
Q

What is the difference between with a giant molecular covalent structure and a simple molecular covalent structure?

A

Giant covalent molecular structure is three dimensional lattice of carbon atoms linked by covalent bonds.

Simple covalent molecular structure is when 2 or more atoms are covalently bonded together to form a distinct unit.

34
Q

What are molecular substances held together by?

A

Covalent bonds.

35
Q

What does a molecular substance show?

A

The number of atoms of each element bonded together in a simple molecule is shown by a molecular substance.

36
Q

How do covalent bonds make atoms more stable?

A

By 2 non-metals sharing electrons in their outer shell they gain a full shell making them stable. The shared electrons create a full outer shell.

37
Q

What is a double bond and how is it formed?

A

Sometimes atoms share more than one pair of electrons to fill their outer shells. In oxygen and carbon dioxide the atoms share two pairs of electrons, to form double bonds.

38
Q

What are the atoms in molecules held together by?

A

By strong electrostatic forces of attraction between the positive nuclei and negative electrons in the bonded atoms. The are also some forces of attraction between the molecules but these are very weak forces of attraction.

39
Q

Why do we use diagrams to represent atoms?

A

Because they are very small about 10 to the power of -10 meters, so we represent them using models.

40
Q

What is meant by the valency of an element?

A

The number of covalent bonds formed between an atom, or the charge number of the ions formed by an atom.

41
Q

What are compounds and how are they formed and what influences their properties?

A

All compounds contain atoms of more than one element, chemically joined together by bonds. The properties of compounds are influenced by its atoms and its types of bonding.

42
Q

What are molecules and and what do they consist of?

A

Some compounds exist as molecules. Molecules are

distinct groups of atoms joined by covalent bonds. They have covalent simple molecular structures. E.g water, H2O.

43
Q

Water is covalently bonded to hydrogen and oxygen. How high is it’s boiling/melting point and why?

A

The covalent bonds in water have strong forces of attraction. However, there are also weak forces of attraction between molecules. These are intermolecular forces. These intermolecular forces hold water molecules together and must be overcome when turning liquid water into gas. Therefore, water has a low boiling point because it doesn’t take much energy to overcome the weak intermolecular forces holding the water molecules together.

44
Q

Why can molecules that are covalently bonded not conduct electricity and not carry current?

A

An electric current is a flow of charged particles. Simple molecules have no overall charge and so cannot carry an electric current. In a covalent bond electrons are shared between atoms. The string forces between the negatively charged electrons and positive nuclei hold the electrons in place so they can’t move in order to carry charge.

45
Q

What is the difference between a monomer and polymer?

A

Monomers are small simple molecules that can be joined in a chain to form a polymer.

Polymers are a chains of monomer. Most polymers contain a chain of carbon atoms.

46
Q

What sort of forces are there in polymer molecules?

A

Polymer molecules can have different lengths. Longer polymers have more intermolecular forces between them. The longer chain also often get tangled up with one another. Because of this longer polymers have higher melting and boiling points than shorter ones.

47
Q

What is a molecule?

A

Groups of atoms joined together by covalent bonds. Molecules can be compounds or elements.

48
Q

What is an allotrope?

A

Different structural forms of the same element. The structure and bonding in different allotropes influence their properties and uses.

49
Q

What are fullerenes? What type of structure are they? What are there properties?

A

-simple molecular structure.
-each carbon atom is covalently bonded to 3 other carbon atoms.
-they can often form tubular or spherical shapes. E.g Bucky balls which are a group of 60 fullerene allotropes forming a sphere.
-They have weak intermolecular forces between molecules and so have low melting point/sublimation point.
-these weak forces also make them soft and slippery.
However, the molecules themselves are very strong due to their covalent bonds.

50
Q

What is graphene? What type of structure are they? What are there properties?

A
  • not a simple molecule
  • consists of a sheet of carbon atoms with no fixed formula.
  • the sheet is just one atoms thick making it the lightest known material, but it’s covalent bonds between molecules make it extremely strong.
  • as its only one atoms thick electrons are free to move across the surface and carry charge so they are therefore good conductors of electricity.
51
Q

Give two examples of giant covalent molecular structures?

A

Graphite and diamond. They both have huge three dimensional network of carbon atoms linked by covalent bonds.

52
Q

Properties of the allotrope graphite:

A
  • it has a high melting point because it has many strong covalent bonds that need to be broken for the solid to melt. Also has string intermolecular forces.
  • graphite has three covalent bonds for each carbon atom.
  • this gives graphite a layered structure meaning it has some free electrons as they are nit all used in the covalent bonds.
  • they electrons form a ‘delocalised sea of electrons’ and can therefore carry charge and conduct electricity.
  • the sheets of carbon are held together by weak forces of attraction. The weak forces allow layers to slide past each other making graphite quite soft and useful as a lubricant.
53
Q

Why is graphite used as electrodes?

A
  • cheap
  • conducts electricity well
  • not reactive
54
Q

Properties of diamond:

A
  • high melting point due to the strong covalent bonds.
  • covalently bonded to 4 other carbon atoms creating a strong 3 dimensional network.
  • very hard because it has a tetrahedral arrangement with string covalent bonds.
  • does not carry current as it has no free electrons as they are all used in covalent bonds meaning it is used as an electrical insulator.
  • very strong and hard so a useful tool to cut things.
55
Q

Common properties of metals:

A
  • good conductors of electricity
  • shiny when polished
  • malleable
  • high density
  • solids with high melting points
56
Q

Common properties of non-metals:

A
  • low melting points when solid, liquid or gas
  • poor conductor of electricity
  • ductile
  • Brittle when solid
  • not usually shiny when solid
57
Q

How is a metallic lattice structure arranged?

A

Atoms in the same element are all the same size and packed closely together in layers to form a lattice structure.

58
Q

Why do metallic structures conduct electricity?

A

Because metals have 1, 2 or 3 electrons in their outer shell. When the bond these electrons are lost and together form a ‘delocalised sea of electrons’ which are free to carry charge and move randomly.
This creates a giant lattice of positive ions surrounded by the delocalised sea of electrons.

59
Q

What is metallic bonding?

A

The electrostatic attraction between the positive metal ions and the negative delocalised electrons. This is why metals have high melting and boiling points because it takes a lot of energy to overcome these very strong forces.

60
Q

How and why are metals malleable and what does this mean?

A

Metals are malleable, this means they can be hammered into shape without shattering. When you hit a metal the layers of ions slide over each other. The sea of electrons hold the ions together so the metal changed shape instead of breaking.

61
Q

How does the sea of electrons enable metals to conduct electricity of the electrons move randomly in different directions?

A

When a potential difference (voltage) is applied between 2 points on a piece of metal the the electrons will flow to the positive side. The flow of electrons transfers energy and forms an electrical current.

62
Q

What is meant by electrical conductivity?

A

How well a substances/ materials conduct electricity. The better they conduct electricity the better their electrical charge.

63
Q

What does the electrical conductivity of a metal depend on?

A

The electrical conductivity of a metal increases as the number of delocalised electrons increases.

64
Q

Give a summary of ionic materials:

A

Found: in most compounds containing a metal and a non-metal.

Bonding: ionic bonds formed by the loss and gain of electrons to produce oppositely charged ions that attract one another.

Structure: billions of ions held together in a lattice structure.

Properties:

  • high melting/boiling points
  • many are soluble in water
  • conduct electricity when molten or dissolved in water
65
Q

Give a summary of simple molecular (covalent) materials:

A

Found: in most non metal elements and compounds.

Bonding: covalent bonds formed when atoms share electrons.

Structure: small distinct groups of atoms.

Properties:

  • low melting/boiling points
  • a few are soluble in water
  • most do not conduct electricity
66
Q

Give a summary of giant molecular (covalent) material:

A

Found: few non metal compounds and elements.

Bonding: covalent bonds form when atoms share pairs of electrons.

Structure: billions of atoms held together in a lattice structure.

Properties:

  • high melting and boiling points
  • insoluble in water
  • most do not conduct electricity (except the allotrope graphite)
67
Q

Give a summary of metallic materials:

A

Found: in all metals.

Bonding: metallic bonds are the electrostatic attraction between
positive metal ions and negative delocalised electrons.

Structure:billions of ions held together in a lattice structure of positive ions in a ‘sea’ of negative delocalised electrons.

Properties:

  • high melting/boiling points
  • insoluble in water
  • conduct electricity when solid or liquid.
68
Q

What do substances with high melting points have and why?

A

They have very strong bonds that need to be broken during melting.

69
Q

What do substances with low melting points have and why?

A

They only have weak forces between molecules that are easily overcome.

70
Q

What is the problem with dot and cross diagrams?

A

These diagrams show how electrons are shared in covalent bonds. However, they do not show the structure formed and they suggest that electrons in different atoms are different, when they are actually the same.

71
Q

What is the problem with metallic models?

A

They show the metals ions held in a lattice and explain why it conducts electricity by the model does not show the atoms will be vibrating all the time.

72
Q

What is the problem with 3D ball and stick models?

A

They show which atoms are joined together and show the shape of the structure but they show the atoms too far apart and there are not really ‘sticks’ inside atoms holding the structure together but rather bonds.

Chemistry (14 decks)

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