Bonding Flashcards

1
Q

Define Metallic Bonding.

A

The strong electrostatic attraction of positive metal ions surrounded by delocalised electrons.

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2
Q

What are the main factors that affect the strength of metallic bonding?

A
  • size
  • charge
  • number of delocalised electrons
  • smaller ion = stronger metallic
  • higher charge = stronger metallic bond
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3
Q

Why is the bonding in Magnesium stronger than in Sodium?

A
  • Mg has a greater charge of 2+
  • Mg has twice as many electrons in the sea of delocalised electrons
  • Mg ions are smaller, meaning there is a greater charge density
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4
Q

What is the structure formed from metallic bonding?

A

Giant metallic lattice.

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5
Q

Outline the conductivity of metals.

A
  • good conductors of heat because the delocalised electrons transfer energy through the metal very efficiently
  • good conductors of electricity because delocalised electrons can flow
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6
Q

Why are metals malleable and ductile and what does this mean?

A

Malleable - can be hammered into shape.

Ductile - can be pulled into wires.

Layers of ions can slide past each other.

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7
Q

How are the melting and boiling points of metals determined?

A

The stronger the metallic bonds, the higher the melting and boiling points.

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8
Q

What are other properties of metals?

A

Insoluble, strong, shiny

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9
Q

How should you write an answer for comparing the melting points of metals?

A
  1. State the structure and describe the bonding - what it occurs between
  2. Compare the strength of attraction being broken
  3. Compare energy required to break attraction in each substance
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10
Q

(Model Answer):

In terms of structure and bonding, explain why Calcium has a higher melting point than Potassium.

A
  1. Both have giant metallic lattice structure, with electrostatic attractions between positive metal ions and delocalised electrons.
  2. Calcium has a greater ionic charge (2+) than potassium (1+) and has more delocalised electrons.
  3. So calcium has stronger metallic bonds and more energy needed to break them
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11
Q

Which metal has a higher melting point, Sodium or Rubidium? Why?

A
  • Both have giant metallic lattices, with attractions between positive ions and delocalised electrons
  • Na+ ions are smaller than Rb+ ions
  • The attraction between ion and delocalised electrons is weaker in Rb+
  • Bonding in Na+ is stronger, more energy needed to break bonds
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12
Q

Define an ionic bond.

A

The strong electrostatic attraction between oppositely charged ions.

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13
Q

What is the structure formed from ionic bonding?

A

Giant Ionic Lattice.

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14
Q

What is the typical melting point of ionic lattices?

A

High.

A lot of energy is needed to break the strong electrostatic attraction between ions.

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15
Q

Describe the electrical conductivity of ionic compounds.

A

Solid ionic compounds cannot conduct electricity because the ions are fixed and cannot flow.

When ionic compounds are molten/aqueous, they do conduct electricity because the ions are free to move.

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16
Q

Why are ionic compounds brittle and can shatter easily?

A

Because if the rows of ions slide past each other, like charges will be next to each other - this causes them to repel and shatter.

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17
Q

What are other properties of ionic compounds?

A
  • Crystalline
  • Solid at room temp
  • Generally good solubility
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18
Q

Describe and explain the electrical conductivity of Sodium Oxide and Sodium in solid and molten states.

A

Sodium conducts in solid and molten states because it has delocalised electrons which are always free to move + carry a current.

Sodium Oxide conducts in a molten state only as ions are free to move + carry a current. In solid state, ions can’t move so can’t carry current.

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19
Q

Define a covalent bond.

A

A shared pair of electrons between 2 atoms.

  • between non-metals
  • atoms share some of their outer shell electrons, giving them both a noble gas configuration
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20
Q

What are the structures which contain covalent bonding?

A

Macromolecular:

  • strong covalent bonds between atoms
  • only in carbon/silicon dioxide

Simple Molecular:

  • strong covalent bonds between atoms
  • weak intermolecular attractions between molecules
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21
Q

What is a coordinate bond?

A

A shared electron pair which have both come from the same atom

  • show it by drawing an arrow from the atom to the atom its being donated to
22
Q

Why is the bond angle for shapes with lone pairs smaller than shapes without lone pairs?

A

Lone pairs repel more strongly than bonding pairs.

23
Q

Explain how the electron pair repulsion theory can be used to deduce the shape of, and the bond angle in, PF3.

A
  • P has 5 electrons in its outer shell
  • With 3 electrons from 3 Flourine atoms, there are a total of 8 electrons in it’s outershell.
  • So 3 bonding pairs, 1 lone pair
  • Electron pairs repel as far as possible
  • Lone pairs repel more than bonding pairs
  • Shape based on tetrahedral
  • Lone pair reduces bond angle from 109.5 to 107 to give trigonal pyramidal shape
24
Q

Define electronegativity.

A

The ability of an atom to attract electron pair density from a covalent bond.

25
Q

What are 3 features of a highly electronegative element?

A
  • high nuclear charge
  • low shielding
  • low atomic radius
26
Q

What is the most electronegative element?

A

Fluorine

  • oxygen and nitrogen are also highly electronegative
27
Q

What happens to electronegativity down a group?

A
  • decreases

- radius and shielding increase

28
Q

What happens to electronegativity across a period?

A
  • increases

- charge increases and radius decreases

29
Q

Describe electronegativity across Period 2.

A
  • number of protons increase
  • shielding stays same
  • ability to attract electrons in covalent bond increases
30
Q

How is the polarity of covalent bonds determined?

A
  • atoms have same charge all around the molecule then its said to be = NON-POLAR
  • atoms have different charge all around molecule then its said to be = POLAR
31
Q

What is the difference between intramolecular forces and intermolecular forces?

A

Intramolecular - forces which hold ATOMS together (metallic, ionic and covalent)

intermolecular forces - forces which hold MOLECULES together (van der waals, dipole dipole and hydrogen)

32
Q

What are dipole-dipole forces?

A

forces of attraction between polar molecules (different charges around molecule)

33
Q

What are Van der waal forces?

A

attractions between polar or non polar molecules.

34
Q

How do Van der Waals forces arise?

A
  • random movement of electrons cause an uneven distribution of electrons
  • causes a temporary dipole in one molecule to induce dipole in neighbouring molecule
  • dipoles attract
35
Q

How is the strength of Van der Waal forces affected?

A

Longer molecules have stronger Van der Waal forces

36
Q

What is Hydrogen bonding?

A

Bonds between hydrogen atom and lone pair on oxygen, nitogen and fluorine atom.

37
Q

Outline Hydrogen bonding in ice.

A
  • The water molecules push apart more than in water
  • So ice expands compare to water,
  • giving it low density meaning it will float on water, instead of sinking.
38
Q

In period 3, silicon has the highest MELTING point but aluminium has the highest BOILING POINT.

Why?

A
  • silicon requires alot of energy to break strong covalent bonds in order to melt it
  • when its melted only a little more energy is required to vapourises it so BP isn’t that much higher than MP
  • however once aluminium is melted then alot more energy is still required to overcome strong electrostatic metallic forces to vapourises
39
Q

What is the shape name and bond angle of a molecule with 2 Bonding pais?

A

Linear

180

40
Q

What is the shape name and bond angle of a molecule with 3 Bonding pairs?

A

Trigonal Planar

120

41
Q

What is the shape name and bond angle of a molecule with 4 Bonding pairs?

A

Tetrahedral

109.5

42
Q

What is the shape name and bond angle of a molecule with 5 Bonding pairs?

A

Trigonal Bipyramidal

90 AND 120

43
Q

What is the shape name and bond angle of a molecule with 6 Bonding pairs?

A

Octahedral

90

44
Q

What is the shape name and bond angle of a molecule with 2 Bonding pairs and 1 Lone pair?

A

V-Shaped

117.5

45
Q

What is the shape name and bond angle of a molecule with 2 Bonding pairs and 2 Lone pairs

A

V-Shaped

104.5

46
Q

What is the shape name and bond angle of a molecule with 3 Bonding pairs and 1 Lone pair?

A

Trigonal Pyramidal

107

47
Q

What is the shape name and bond angle of a molecule with 2 Bonding pairs and 3 Lone pairs?

A

Linear

180

48
Q

What is the shape name and bond angle of a molecule with 4 Bonding pairs and 1 Lone pair?

A

Seesaw Molecules

89 AND 119

49
Q

What is the shape name and bond angle of a molecule with 3 Bonding pairs and 2 Lone pairs?

A

T-Shaped

89

50
Q

What is the shape name and bond angle of a molecule with 4 Bonding pairs and 2 Lone pairs?

A

Square Planar

90

51
Q

What is the shape name and bond angle of a molecule with 5 Bonding pairs and 1 Lone pair?

A

Square Pyramidal

89