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Chemistry A level (Edexcel) > TOPIC 2 - Chemical bonding and structure > Flashcards

TOPIC 2 - Chemical bonding and structure Flashcards

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1
Q

What is the formula and charge of the hydroxide ion?

A

OH-

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2
Q

What is the formula and charge of the nitrate ion?

A

NO3-

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3
Q

What is the formula and charge of the ammonium ion?

A

NH4+

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4
Q

What is the formula and charge of the sulfate ion?

A

SO42-

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5
Q

What is the formula and charge of the carbonate ion?

A

CO32-

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6
Q

Why do ionic substances dissolve in water?

A

Water is a polar molecules. The partially positive hydrogens and partially positive oxygens in water will be atracted to the oppositely charged ions and so will break the lattice.

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7
Q

Why do ionic substances conduct electricity when molten or dissolved?

A

Ions are free to move.

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8
Q

Why do ionic compounds have high mpt/bpt?

A

Many, strong electrostatic forces of attraction between oppositely charged ions require lots of energy to break down.

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9
Q

Why are ionic compounds brittle?

A

When struck, the layers of ions slide past each other and oppositely charged ions are forced together. The ions repel and the structure breaks appart.

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10
Q

How does the size of charge in ionic compounds affects the bpt/mpt?

A

Bigger charge, so bigger charge density and so stronger electrostatic forces of attraction and so more energy is required to overcome those forces and so have a higher bpt/mpt.

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11
Q

How does the size of the ion affect the mpt/bpt in an ionic substance?

A

Smaller ions, ions are closer and so there’s a bigger charge density, therefore there are stronger electrostatic forces of attraction and so more energy is required to overcome them and so higher bpt/mpt.

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12
Q

What are isoelectronic ions?

A

Different atoms with the same number of electrons.

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13
Q

How does the radius of isoelectronic ions vary as atomic number increases?

A

Decreases.

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14
Q

What evidence is there for charged ions?

A

When you place green Copper(II)Chromate(VI) on a wet filter paper and apply a current, positive Cu2+ ions (blue) are seen moving towards -ve cathode while negative Cr2O42- ions (yellow) move towards the anode.

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15
Q

How does electron density affect bond length and bond enthalpy?

A

Higher the electron density, the shorter the bond length and so higher bond enthalpy.

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16
Q

What is the general rule for calculating the bond angles in molecules with lone pairs of electrons?

A

Subtract 2.5 from the basic shape for every lone pair. To find the basic structure, assume the lone pairs are bonding pairs.

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17
Q

What is the molecular shape for 2 bond pairs and 0 lone pairs?

A

Linear. i.e. BeCl2

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18
Q

What is the molecular shape for 3 bond pairs and 0 lone pairs?

A

Trigonal Planar. i.e. BF3

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19
Q

What is the molecular shape for 4 bond pairs and 0 lone pairs?

A

Tetrahedral. i.e. CH4

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20
Q

What is the molecular shape for 5 bond pairs and 0 lone pairs?

A

Trigonal Bipyramidal. i.e. PCl5

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21
Q

What is the molecular shape for 6 bond pairs and 0 lone pairs?

A

Octahedral. i.e. SF6

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22
Q

What is the molecular shape for 2 bond pairs and 1 lone pair?

A

Trigonal pyramidal. i.e. NH3

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23
Q

What is the molecular shape for 2 bond pairs and 2 lone pairs?

A

Bent. i.e. H2O

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24
Q

What is the molecular shape for 3 bond pairs and 2 lone pairs?

A

Distorted T. i.e. ClF3

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25
Q

What is the molecular shape for 4 bond pairs and 1 lone pair?

A

Seesaw. i.e. SF4

26
Q

What is the molecular shape for 5 bond pairs and 1 lone pair?

A

Square pyramidal. i.e. IF5

27
Q

What is the molecular shape for 4 bond pairs and 2 lone pairs?

A

Square planar. i.e. XeF4

28
Q

What is the bonding structure of graphite?

A

Layers in which each carbon is bonded 3 times. The 4th electron is delocalised. The delocalised electrons keep the layers together.

29
Q

What allows layers in graphite to slide easily?

A

There are weak forces of attraction between layers.

30
Q

What allows graphite to have low density?

A

Layers are far apart.

31
Q

What makes graphite have a high bpt/mpt?

A

Lots of strong covalent bond in the macromolecular structure.

32
Q

What makes graphite insoluble?

A

Strong covalent bonds are difficult to break.

33
Q

What allows graphite to conduct electricity?

A

Delocalised electrons between layers are able to move.

34
Q

What is the bonding structure of diamond?

A

Giant macromolecular structure where each carbon is bonded 4 times. (similar to SiO2)

35
Q

What makes diamond a heat conductor?

A

Highly packed, rigid arrangement of atoms.

36
Q

What makes diamond insoluble?

A

Very strong covalent bonds which are difficult to overcome.

37
Q

What makes diamond have a high bpt/mpt?

A

Strong covalent bonds.

38
Q

Why can’t diamond conduct electricty?

A

It has no delocalised electrons.

39
Q

What is the bonding structure in graphene?

A

1 layer of graphite: 1 atom thick layer of hexagonal carbon rings (each carbon is bonded 3 times).

40
Q

What makes graphene an electrical conductor?

A

It has delocalised electrons.

41
Q

What makes graphene strong?

A

Strong covalent bonds.

42
Q

What makes graphene lightweight and transparent?

A

It is 1 atom thick.

43
Q

What are the uses of graphene?

A
  • Aircraft shells
  • supercomputers
  • smartphone screens
44
Q

What makes metals good thermal conductor?

A

delocalised electrns can transfer kinetic energy.

45
Q

What makes metals good electrical conductors?

A

Delocalised electrons can move.

46
Q

What makes metals have a high mpt/bpt?

A

Strong electrostatic forces of attraction between between ions and delocalised electrons.

47
Q

What makes metals insoluble?

A

Metallic bonds are too strong to break.

48
Q

What makes metals malleable and ductile?

A

Layers can slide and still be attracted to the delocalised electrons, which holds them together.

49
Q

What is electronegativity?

A

The ability for an atom to attract electrons towards itself in a covalent bond.

50
Q

What is the trend of electronegativity in the periodic table?

A

The further up (smaller atom) and further right (higher nuclear charge), the more electronegativity there is.

51
Q

Which element is the most electronegative?

A

Fluorine.

52
Q

How does the difference in electronegativity affect the polarity of a bond?

A

The bigger the difference in electronegativity between two atoms in a bond, the more polar the bond is (the bond is ionic when the difference is even higher)

53
Q

Which scale measures electronegativity?

A

The Pauling scale.

54
Q

Are all molecules with polar bonds polar molecules?

A

No. Only the ones with uneven distribution of charge (not symmetrical).

55
Q

What is the order of the different intermolecular forces from strongest to weakest?

A
  • Hydrogen bonding
  • permanent dipole-dipole interactions
  • London forces
56
Q

How does london forces vary with the size of the molecule?

A

Generally, the bigger the molecule, the stronger the london forces.

57
Q

How does branching affect london forces

A

Branching decreases london forces as molecules can’t get closer together.

58
Q

When do hydrogen bond occur?

A

With molecules that have a bond between H and O/N/F.

59
Q

Why is ice less dense than water?

A

Ice is a regular structure of water molecules held together by hydrogen bonding.

Molecules are further apart.

Therefore it is less dense.

60
Q

Why is HF the highest?

A

It can hydrogen bond.

61
Q

Why is there an increae from HCl to HI?

A

Bigger halides, so more electrons so bigger london forces. This offsets the decreasing permanent dipole-dipole interactions.

62
Q

Why does Al2O3 not dissolve?

A

Ionic bonding is too strong

Chemistry A level (Edexcel) (19 decks)

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