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A-Level Chemistry Edexcel > 2A: Bonding > Flashcards

2A: Bonding Flashcards

Use PPQs for spec points: 4, 8, 12, 19

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1
Q

What is ionic bonding?

A

The strong electrostatic attraction between oppositely charged ions

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2
Q

How do ionic radius and ionic charge affect the strength of ionic bonding?

A
  • Smaller ionic radius and greater ionic charge
  • So greater charge density
  • So stronger ionic bonding
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3
Q

Describe the formation of ions in terms of electron loss or gain.

A

Loss of electrons forms positive ions.

Gain of electrons forms negative ions.

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4
Q

Explain the trend in ionic radius down a group.

A

Ionic radius increases, because more electron shells.

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5
Q

Explain the trend in ionic radius for isoelectronic ions.

A

Ions with a higher nuclear charge have a smaller ionic radius.

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6
Q

Describe the experiment to show the migration of ions.

A

Ionic compound on damp filter paper with oppositely charged electrodes.
The opposite ions migrate towards the electrodes.

Proves the existence of ions.

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7
Q

What is covalent bonding

A

The strong electrostatic attraction between two nuclei and the shared pair of electrons between them

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8
Q

Explain the relationship between bond lengths and bond strengths for covalent bonds?

A

Shorter bond = stronger bond,
because electrons are closer to the nucleus

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9
Q

State and explain the trend in X-X bond length as you go down group 7.

A

More electron shells,
so more shielding,
so weaker attraction between the nuclei and the bonding electrons,
so longer bond.

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10
Q

What determines the shape of a simple molecule or ion?

A

The repulsion between the electron pairs that surround a central atom.
Electron pairs will take a position where repulsion is minimised.

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11
Q

Shape and bond angles of BeCl2

A

Linear
180

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12
Q

Shape and bond angles of BCl3

A

Trigonal planar
120

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13
Q

Shape and bond angles of CH4

A

Tetrahedral
109.5

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14
Q

Shape and bond angles of NH3

A

Trigonal Pyramidal
107

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15
Q

Shape and bond angle of NH4+

A

Tetrahedral
109.5

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16
Q

Shape and bond angle of H2O

A

Bent
104.5

17
Q

Shape and bond angles of PCl5

A

Trigonal Bipyramidal
120 and 90

18
Q

Shape and bond angle of SF6

A

Octahedral
90

19
Q

What is electronegativity?

A

The ability of an atom to attract the bonding electrons in a covalent bond

20
Q

How is a dipole formed?

A

When bonding atoms have a large difference in electronegativity, they attract electrons unequally, and one gets a slight positive charge and the other a slight negative charge.

21
Q

What is a polar molecule?

A

A molecule with polar bonds creating an overall dipole.

22
Q

How do you practically check if a substance contains polar molecules?

A

Electrostatic charge next to a jet of liquid.
Polar molecules will be attracted.

23
Q

Describe London Forces.

A

Instantaneous dipole - induced dipole.
Caused by an instantaneous imbalance of electrons in the molecule.
The resultant dipole induces a dipole in a nearby atom or molecule.

Strength increases with number of electrons.

24
Q

Describe permanent dipole attractions.

A

Two molecules with permanent overall dipoles.
Attraction between the positive charge in one molecule and the negative charge in the other.

25
Q

Describe a diagram to show hydrogen bonding.

A

Lone pair on the O,
delta+ on H and delta- on O,
dashed line between H and the lone pair

26
Q

What is needed for a Hydrogen Bond to form?

A
  • A large dipole between a H atom and a highly electronegative atom (eg O, N or F)
    • A small H atom that can get very close to other molecules
    • A lone pair of electrons on the O, N or F atom that the positively charged H atom can line up with
27
Q

Explain the melting and boiling points of water.

A

Relatively high temperatures.
Each molecule has 2 hydrogens connected to an oxygen, so it can form 2 hydrogen bonds with other water molecules.

28
Q

Explain the density of ice compared to water.

A

Lower density.
As water freezes, the hydrogen bonds pull the water molecules into fixed positions in a comparatively open lattice.

29
Q

State and explain the trends in boiling temperatures of alkanes with increasing chain length.

A

As chain length increases,
there are more electrons,
so London forces are stronger,
so boiling point increases.

30
Q

State and explain the effect of branching in the carbon chain on the boiling temperatures of alkanes

A

Molecules cannot get as close together,
so London forces are weaker,
so boiling point is decreased.

31
Q

State and explain the volatility of alcohols compared to alkanes with a similar number of electrons.

A

The -OH group causes hydrogen bonding,
so boiling point is much higher than alkanes,
so volatility is relatively low.

32
Q

State and explain the trends in boiling temperatures of the hydrogen halides, HF to HI.

A

HF has hydrogen bonding, so boiling point is highest.

Down the group from HCl to HI,
number of electrons increases
so London forces are stronger,
so boiling point increases.

33
Q

Explain why some ionic compounds dissolve in water.

A

The polar water molecules are attracted to the charged ions.
The water molecules hydrate the ions and break the ionic bonds in the compound.

34
Q

Explain why simple alcohols dissolve in water.

A

Alcohols form hydrogen bonds between molecules.
Alcohols also form hydrogen bonds with water molecules.
Bonds formed are similar to bonds broken.

35
Q

Explain why polar molecules such as halogenoalkanes are insoluble in water.

A

They are unable to form hydrogen bonds with water.

36
Q

What compounds would you dissolve in non-aqueous solvents?

A

Compounds that have similar intermolecular forces to those in the solvent.

37
Q

What is metallic bonding?

A

The strong electrostatic attraction between metal ions and the delocalised electrons

38
Q

What colours would be observed after the electrolysis of copper(II) chromate(VI)?

A

Cathode: Blue (copper ions)
Anode: Yellow (chromate ions)

A-Level Chemistry Edexcel (34 decks)

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