3.1 - 3.7 Bonding Flashcards

1
Q

What is an ionic bond?

A

The electrostatic attraction between oppositely charged ions

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2
Q

Positive ion

A

Cation

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3
Q

Negative ion

A

Anion

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4
Q

What is a covalent bond?

A

A shared pair of electrons. The electron pair is attracted to both nuclei so resist separation.

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5
Q

What is a co-ordinate bond?

A

A covalent bond where both electrons in the shared pair originate from the same atom

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6
Q

What is metallic bonding?

A

The attraction between positive metal atoms and the surrounding delocalised sea of electrons

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7
Q

What is electronegativity?

A

The power of an atom to attract the pair of electrons in a covalent bond

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8
Q

Nuclear charge up = electronegativity ?

A

Electronegativity up

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9
Q

Atomic radius up = shielding ? = electronegativity ?

A

Shielding up = electronegativity down

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10
Q

What is used to measure electronegativity?

A

The Pauling scale

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11
Q

What happens to electronegativity across a period?

A
  • Increases
  • Same no. of energy levels BUT
  • Increasing no. of protons/nuclear charge
  • Decreasing atomic radius
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12
Q

What happens to electronegativity up a group?

A
  • Increases
  • Fewer energy level in use
  • Less shielding
  • Decreasing atomic radius
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13
Q

What is a polar molecule?

A

One in which the electron density across the whole molecule is unevenly distributed

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14
Q

What is a permanent dipole?

A

When one side of the molecule is permanently more negative, happens when a molecule is not symmetrical

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15
Q

What are the 3 main types of inter-molecular forces?

A
  • Dipole-dipole interactions
  • Hydrogen bonding
  • Van der Waal’s forces
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16
Q

What are dipole-dipole interactions?

A
  • Attractive forces between polar molecules

- Whatever their starting position, molecules will ‘flip’ to attract

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17
Q

What are hydrogen bonds?

A
  • Not a bond, an inter-molecular force

- Only takes place when H bonded to O, F or N with at least one lone pair

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18
Q

What are Van der Waal’s forces?

A
  • Also known as temporary dipole-induced dipole interactions
  • Caused by the movement of electrons so the more electrons there are the stronger the force
  • Exist between all molecules at all times, in addition to any other forces
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19
Q

List the three main inter-molecular forces from weakest to strongest

A
  • Van der Waal’s
  • Dipole-dipole
  • Hydrogen bonding
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20
Q

Describe the particles in a solid

A

Regular, close, vibrate about a fixed position

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21
Q

Describe the particles in a liquid

A

Random, close, can move past each other

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22
Q

Describe the particles in a gas

A

Far apart, rapid and random motion

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23
Q

What is the name for the energy required to boil a liquid?

A

Enthalpy of vaporisation

24
Q

What is the name for the energy required to melt a solid?

A

Enthalpy of fusion

25
Q

What are the four types of crystal structure?

A
  • Ionic
  • Metallic
  • Molecular (simple covalent)
  • Macromolecular (giant covalent)
26
Q

What is an ionic crystal?

A

Positive and negative ions held together in a giant ionic lattice by strong electrostatic attraction between oppositely charge ions

27
Q

Describe and explain the melting points of ionic compounds

A
  • High

- Strong electrostatic attraction between oppositely charged ions

28
Q

Describe and explain the electrical conductivity properties of ionic compounds

A
  • Does not conduct when solid
  • No ions (charged particles) free to move
  • Does conduct when molten or in solution
  • Ions free to move and carry charge
29
Q

Describe and explain the physical properties of ionic compounds

A
  • Hard but brittle

- A force can move the ions and produce contact between like charges causing them to repel

30
Q

Describe and explain the solubility of ionic compounds

A
  • Often dissolve in water

- Ions become solvated and surrounded by water molecules

31
Q

What is a metallic crystal?

A

A giant lattice of positive ions held together by a sea of delocalised electrons

32
Q

Describe and explain the melting points of metals

A
  • High melting and boiling points

- Strong electrostatic attraction between metal ions and delocalised sea of electrons

33
Q

Describe and explain the electrical conductivity of metals

A
  • Conduct in all states

- Delocalised electrons free to move and carry charge

34
Q

Describe and explain the physical properties of metals

A
  • Malleable and ductile

- Metal ions can slide past each other while retaining their lattice structure and metallic properties

35
Q

Describe and explain the solubility of metals

A
  • Insoluble in water

- Metallic bonds are too strong for water so overcome so metal ions cannot become solvated

36
Q

What is a molecular crystal?

A

Individual molecules held together by weak intermolecular forces

37
Q

Describe and explain the melting points of molecular solids

A
  • Low melting points

- Weak intermolecular forces (VDW) do not require much energy to overcome

38
Q

Describe and explain the physical properties of molecular solids

A
  • Soft and easily breakable

- Weak intermolecular forces (VDW) do not require much energy to overcome

39
Q

Describe and explain the electrical conductivity of molecular solids

A
  • Never conduct electricity

- No charged particles free to move

40
Q

What is a macromolecular crystal?

A

A giant arrangement of atoms joined by covalent bonds

41
Q

Describe and explain the melting point of diamond

A
  • Very high (3,000C +)

- Strong covalent bonds require a lot of energy to break

42
Q

Describe and explain the physical properties of diamond

A
  • Very hard

- Strong covalent bonds require a lot of energy to break

43
Q

Describe and explain the melting point of graphite

A
  • Very high (3,000C +)

- Strong covalent bonds require a lot of energy to break

44
Q

Describe and explain the physical properties of graphite

A
  • Soft, flaky and slippery

- Layers slide over each other because of delocalised electrons between layers

45
Q

Describe and explain the electrical conductivity of graphite

A
  • Conducts electricity

- Delocalised electrons free to move and carry charge

46
Q

How does the bond angle change when a molecule’s loan pair forms a hydrogen bond?

A
  • Increases
  • Loan pair more like bonding pair so does not repel so strongly
47
Q

How can electronegativity values be used to predict whether a given chloride is likely to be ionic or covalent?

A

Large difference in electronegativity = Ionic

Small difference in electronegativity = Covalent

48
Q

Explain the formation of hydrogen bonding between protein molecules

A
  • C=O and N-H bonds are polar
  • O more electronegative than C, N more electronegative than H
  • H-bonding between Hpartial+ and Opartial- of different molecules
  • Using lone pair of electrons from oxygen
49
Q

Why does the boiling point of fluorine compounds not fit into other trends?

A
  • Unexpectedly high
  • Due to hydrogen bonding
  • Caused by large differences in electronegativity of fluorine and other element
50
Q

Give an equation for a reaction in which a co-ordinate bond is formed

A

NH₃ + H⁺ → NH4⁺

51
Q

Why is aluminium chloride covalent rather than ionic?

A
  • Smaller electronegativity difference

- So more equal sharing

52
Q

How do you know if two atoms will bond ionically of covalently?

A

Ionic = Big electronegativity difference

Covalent = Small electronegativity difference

53
Q

How does hydrogen bonding work?

A

Hpartial+ attracted to lone pair of another partially negative molecule

54
Q

Define polar bond

A

A bond where the bonding pair is shared unequally

55
Q

Why does a lone pair of electrons repel more strongly than a bonding pair?

A

More compact