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Chemistry A-Level > 2.2.2 Bonding and structure > Flashcards

2.2.2 Bonding and structure Flashcards

1
Q

What are the 3 main types of chemical bonds?

A
  • Ionic
  • Covalent
  • Metallic
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2
Q

Define ionic bonding?

A

The electrostatic attraction between positive and negative ions

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3
Q

Give an example of an ionically bonded lattice

A

NaCl (sodium chloride - salt)

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4
Q

Define covalent bonding?

A

Electrostatic attraction between a shared pair of electrons and the nuclei

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5
Q

Define metallic bonding?

A

Electrostatic attraction between the positve metal ions and the sea of delocalised electrons

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6
Q

Electrons in which shell are represented in a dot and cross diagram?

A

The outer shell

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7
Q

Why do giant ionic lattices conduct electricity when liquid but not when solid?

A

In solid state the ions are held in fixed positions and thus cannot move. When they are in liquid state the ions are mobile and thus can freely carry the charge

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8
Q

Giant ionic lattices have high or low melting and boiling points? Explain your answer

A

They have high melting and boiling point because a large amount of energy is required to overcome the electrostatic bonds

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9
Q

In what type of solvents do ionic lattices dissolve?

A

Polar solvents

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10
Q

Why are ionic compounds soluble in water?

A

Water has a polar bond. Hydrogen atoms have a δ⁺ charge and oxygen atoms have a δ⁻ charge. These charges are able to attract charged ions.

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11
Q

What is it called when atoms are bonded by a single pair of shared electrons?

A

Single bond

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12
Q

How many covalent bonds does carbon form?

A

4

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13
Q

How many covalent bonds does oxygen form?

A

2

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14
Q

What is a lone pair?

A

Electrons in the outer shell that are not involved in bonding

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15
Q

What is formed when atoms share two pairs of electrons?

A

double bond

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16
Q

What is formed when atoms share three pairs of electrons?

A

Triple bond

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17
Q

What is the average bond enthalpy?

A

Measure of average energy needed to break the bond

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18
Q

What is a dative covalent bond?

A

A bond where both of the shared electrons are supplied by one atom

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19
Q

How are oxonium ions formed?

A

Formed when acid is added to water

H₃O⁺

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20
Q

What does expansion of the octet mean?

A

When a bonded atom has more than 8 electrons in the outer shell

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21
Q

What are the types of covalent structure?

A
  • Simple molecular lattice

- Giant covalent lattice

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22
Q

Describe the bonding in simple molecular structures

A

Atoms within the same molecule are held by strong covalent bonds and different molecules are held by strong covalent bonds and different molecules are held by weak intermolecular forces

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23
Q

Why do simple molecular structures have low melting and boiling point?

A

Small amount of energy is enough to overcome the intermolecular forces

24
Q

Can simple molecular structures conduct electricity?

A

No, they are non conductors

25
Q

Why do simple molecular structures not conduct electricity?

A

They have no free charged particle to mave around

26
Q

Simple molecular structures dissolve in what type of solvent?

A

Non polar solvents

27
Q

Give an example of a giant covalent structure

A
  • Diamond
  • Graphite
  • Silicon dioxide
28
Q

What are some properties of giant covalent structures?

A
  • High melting and boiling points
  • Non conductors of electricity except graphite
  • Insoluble in polar and non polar solvents
29
Q

How does graphite conduct electricty?

A

Delocalised electrons present between the layers are able to move freely carrying the charge

30
Q

Why do giant covalent structures have high melting and boiling points?

A

Strong covalent bonds within the molecules need to be broken which requires lots of energy

31
Q

Describe the structure of a diamond

A

3D tetrahedral structure of C atoms with each C atom bonded to four others

32
Q

What does the shape of a molecule depend on?

A
  • Number of electron pairs in the outer shell

- Number of these electrons which are bonded and lone pairs

33
Q

What is the shape and bond angle in a shape with 2 bonded pairs and 0 lone pairs

A

Linear

180°

34
Q

What is the shape and bond angle in a shape with 3 bonded pairs and 0 lone pairs

A

Trigonal planar

120°

35
Q

What is the shape and bond angle in a shape with 4 bonded pairs and 0 lone pairs

A

Tetrahedral

109.5°

36
Q

What is the shape and bond angle in a shape with 5 bonded pairs and 0 lone pairs

A

Trigonal bipyramidal

90° and 120°

37
Q

What is the shape and bond angle in a shape with 6 bonded pairs and 0 lone pairs

A

Octahedral

90°

38
Q

What is the shape and bond angle in a shape with 3 bonded pairs and 1 lone pairs

A

Pyramidal

107°

39
Q

What is the shape and bond angle in a shape with 2 bonded pairs and 2 lone pairs

A

Non linear

104.5°

40
Q

By how many degrees does each lone pair reduce the bond angle

A

2.5°

41
Q

Define electronegativity

A

The abilty of an atom to attract the pair of electrons (the electron density) in a covalent bond

42
Q

In which direction of the periodic table does electronegativity increase?

A

Top right, towards fluorine

43
Q

What is meant when the bond is non polar?

A

The electrons in the bond are evenly distributed

44
Q

What is the most electronegative element?

A

Fluorine

45
Q

How is a polar bond formed?

A

Bonding atoms have different electronegativities

46
Q

Why is H₂O polar whereas CO₂ is non polar?

A

CO₂ is a symetrical molecule so there is no overall dipole

47
Q

What is meant by intermolecular force

A

Attractive forces between neighbouring molecules

48
Q

What are the two types of intermolecular forces?

A
  • Hydrogen bonding

- Van der Waals’ forces

49
Q

What is the strongest type of intermolecular force?

A

Hydrogen bonding

50
Q

Describe London forces?

A
  • Londone forces are caused by random movements of electrons
  • This leads to instantaneous dipoles
  • Instantaneous dipole induces a dipole in nearby molecules
  • Induced dipoles attract one another
51
Q

Are London forces greater in smaller or larger molecules?

A

Larger due to more electrons

52
Q

Does boiling point increase or decrease down the noble gas group? Why?

A

Boiling point increases because the number of electrons increases hence the strength of London forces also increases

53
Q

What conditions are needed for hydrogen bonding to occur?

A

O-H, N-H or F-H bond , lone pair of electrons on O, F, N because O, N, and F are highly electronegative, H nucleus is left exposed
Strong forces of attraction between H nucleus and lone pair of electrons on O, N, F

54
Q

Why is ice less dense than liquid water?

A
  • In ice the water molecules are arranged in orderly patterns. It has an open lattice with hydrogen bonds
  • In water the lattice is collapsed and the molecules are closer toegether
55
Q

Why does water have a higher melting/ boiling point than expected?

A

Hydrogen bonds are stronger than other intermolecular forces so extra strength is required to overcome the forces

Chemistry A-Level (35 decks)

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