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OCR A level Chemistry > Bonding and structure- bonding > Flashcards

Bonding and structure- bonding Flashcards

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1
Q

What is meant by the term ionic bond?

A

The electrostatic attraction between positively and negatively charged ions

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2
Q

What is meant by the term covalent bond?

A

The electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

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3
Q

What is a molecule?

A

A small group of atoms bonded together by covalent bonds

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4
Q

What are lone pairs?

A

A pair of electrons in the outer shell NOT used in conding

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5
Q

What is a dative covalent bond?

A

A shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only

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6
Q

Why do metals have high melting and boiling points?

A
  • Strong electrostatic attraction between metal cations and delocalised electrons
  • Requires a lot of energy to break
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7
Q

Why are metals good electrical conductors when solid?

A

-Delocalised electrons can move and carry charge

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8
Q

Why are metals good electrical conductors when molten?

A

-Delocalised electrons and metal cations can move and carry charge

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9
Q

Why are metals insoluble in water?

A
  • strong electrostatic attraction between metal cations and delocalised electrons which require a lot of energy to break
  • This energy is not avaliable
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10
Q

Why do the melting points of metals increase in order from sodium, magnesium, aluminium?

A
  • the charge on the metal ion increases from 1+, to 2
    +, to 3+
    -the no. delocalised electrons per ion increases
    -this results in a stronger electrostatic attraction between metal ions and delocalised electrons
    -more energy is necessary to break them
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11
Q

Out of sodium, magnesium, and aluminium which would you expect to be the best conductor of electricity and why?

A

Aluminium

  • greatest no. delocalised electrons per metal ion
  • greatest capacity for carrying charge
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12
Q

How does the model of metallic bonding explain why metals are ductile and malleable?

A

-layers of ions can slide over each other easily

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13
Q

What metals are present in the following alloys?

i) Brass
ii) Stainless steel

A

i) Zinc and Copper

ii) Iron and Chromium

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14
Q

How does an alloy make a metal harder?

A
  • Each metal ion is a slightly different size

- So layers of ions do not slide over each other so easily

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15
Q

What does ductile mean?

A

Able to be drawn into a wire

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16
Q

Define ion

A

A positively or negatively charged atom or (covalently bonded) group of atoms where the number of protons differs from the number of electrons

17
Q

Define giant ionic lattice

A

A 3D structure of charged ions bonded together by strong ionic bonds

18
Q

Define simple molecular lattice

A

A 3D structure of molecules bonded together by weak intermolecular forces

19
Q

Define giant covalent lattice

A

A 3D structure of atoms bonded together by strong covalent bonds

20
Q

Define giant metallic lattice

A

A 3D structure of positive ions and delocalised electrons held together by strong metallic bonds

21
Q

Why do ionic substances have high melting and boiling points?

A
  • strong electrostatic attractions between anions and cations
  • require a lot of energy to overcome
22
Q

Why are ionic substances non-conductors of electricity when solid?

A
  • the ions are fixed in the lattice

- so cannot move and carry charge

23
Q

Why are ionic substances good electrical conductors when in solution or molten?

A
  • the ions are no longer fixed in the lattice

- and so are free to move and carry charge

24
Q

Why do ionic substances generally have good solubility in water?

A
  • oxygen atoms in water are attracted to and surround the positive ions
  • hydrogen atoms in water are attracted to and surround the negative ions
  • this results in the breaking down of the ionic lattice and the compound dissolving
25
Q

Why are ionic substances brittle?

A
  • slight movement of the layer of ions bring positive ions next to positive ions and negative ions next to negative ions
  • this causes repulsion and the structure breaking apart
26
Q

What two factors affect the melting point of an ionic substance?

A
  • IONIC radius

- Charge on the ions

27
Q

What are the boiling and melting points of simple molecular substances like?
why?

A

Low

-because weak intermolecular forces between molecules require little energy to break

28
Q

Are simple molecular substances good electrical conductors? Why?

A

No

-they have no mobile charge carriers

29
Q

Are simple molecular substances soluble in non-polar solvents? Why?

A

Yes

  • solvent molecules are able to form similar intermolecular forces with molecules
  • weak intermolecular forces do not need much energy to overcome
30
Q

What are the boiling and melting points of giant covalent substances like?
why?

A

High

-strong electrostatic attractions must be overcome which requires a lot of energy

31
Q

Are giant covalent substances good electrical conductors? Why?

A

No

-they do not contain and free mobile charge carriers

32
Q

Are giant covalent substances soluble in non-polar solvents? Why?

A

No

-strong covalent bonds between atoms require too much energy to be overcome

33
Q

Can diamond conduct electricity? Why?

A

No

Contains no mobile charge carriers

34
Q

Can graphite conduct electricity? Why?

A

Yes

-contains delocalised electrons in layers which are free to move and carry charge

35
Q

How hard is diamond? Why?

A

Very hard

  • tetrahedral structure of atoms means forces are spread through the structure
  • strong covalent bonds require a lot of energy to be broken
36
Q

How hard is graphite? Why?

A

Soft

  • weak intermolecular forces require little energy to overcome and so can be easily broken
  • layers can slide over each other
37
Q

Are simple molecular substances often soluble in water?

A

Yes

OCR A level Chemistry (30 decks)

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