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Chemisty A level > structure, bonding and physical properties > Flashcards

structure, bonding and physical properties Flashcards

1
Q

What structure does a metallic substance have?

A

giant metallic lattic

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2
Q

What structure does an ionic substance have?

A

giant ionic lattice structures

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3
Q

What structures does a covalent substance have?

A

giant covalent lattice structure
simple covalent lattice structure

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4
Q

What is a giant metallic lattic structure?

A

metal atoms form a lattice held together by metallic bonding

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5
Q

Describe metallic bonding in terms of electrons and orbitals.

A

the outer orbitals of the metal atoms overlap to some extent, so the metal can be thought of a lattice of positive ions surrounded by a ‘sea’ of delocalised electrons

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6
Q

What is metallic bonding?

A

the attraction between a lattice of positive metal ions and a sea of delocalised electrons

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7
Q

Why are metals good conductors of electricity?

A

the delocalised electrons are mobile
the more delocalised electrons there is the higher the conductivity

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8
Q

Why do metals have a relatively high melting point?

A

a lot of energy is needed to break the strong metallic bonding
more delocalised electrons = the stronger the bond

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9
Q

What are the key physical properties of metals?

A

conduction of heat, malleable, ductile, shiny, sonorous

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10
Q

How is the structure maintained in a giant metallic lattice?

A

the positive charges repel each other which keeps the cations fixed in position

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11
Q

What affects the BP and MP in giant metallic lattices?

A

the charge of the cations and the size of the cations
the larger the atomic radius = lower MP

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12
Q

Why are metallic lattices insoluble in water?

A

the polar H2O and the charges in the metallic structure would lead to a reaction rather than dissolving

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13
Q

How can you strengthen metals?

A

increase delocalised e-
increase positive charge of metal atoms
decrease the size of metal ions = tigher lattice

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14
Q

What is a giant ionic lattice?

A

alternating arrangement of positive and negative ions

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15
Q

What is the bond in a giant ionic lattice?

A

electrostatic attraction between oppositely charged particles

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16
Q

Why do giant ionic substances have a high MP and BP?

A

lots of energy needed to break string ionic bonds
if the charge increases then the bond strength also increases

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17
Q

Why are giant ionic lattices soluble in water?

A

the water can form ion-dipole forces with dissolved ions to compensate for the loss of ionic bonds

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18
Q

Why can giant ionic lattices conduct electricity when molten or aqueous?

A

the ions are mobile

19
Q

What are covalent substances?

A

mainly non-metallic elements and compounds involing only non-metals

20
Q

Which type of covalent structure is more common?

A

simple molecular

21
Q

What are simple molecular structures?

A

each molecule is made up of a defined no. of atoms, covalently bonded together. the molecules are attracted together by intermolecular forces

22
Q

Why do simple molecular substances have a low MP and BP?

A

only the intermolecular forces have to be broken which are relatively weak
the covalent bonds are strong but they remain intact - has no affect

23
Q

Why do simple molecular substances have a low electrical conductivity?

A

they have no mobile electrons or ions

24
Q

Usually simple molecular structures have low solubility in water, what 2 conditions make them more soluble in water?

A
  1. they react with water to form ions eg: hydrogen chloride —> H+ and CL-
  2. they can form hydrogen bonds with water
25
Q

What allows simple molecular substances to form h bonds with water?

A

some of the hydrogen bonds between water molecules need to be broken
the energy needed for this endothermic process comes from the exothermic process of forming H bonds at the same time

26
Q

What simple molecular compounds have high solubility in water?

A

compounds with OH or NH groups

27
Q

What is a giant covalent structure?

A

the covalent bonds extend throughout the whole crystal, usually in three dimensions

28
Q

Why do giant covalent lattices have high MP and BP?

A

due to covalent bonds acting in all directions and they need to be broken

29
Q

Describe diamond’s structure

A

each carbon atom is covalently bonded to 4 other carbon atoms
tetrahedral - 109.5

30
Q

What are diamond’s properties?

A

very high MP = C-C bonds need to be broken
very hard = giant lattice holding atoms together
non-conductor = no mobile electrons or ions

31
Q

What are diamond’s uses?

A

drill bits
saw blades
jewellery

32
Q

Describe Graphite’s structure?

A

the covalent bonding only extends in two dimensions, giving layers which are held together by induced dipole- dipole forces
each c atom is bonded to 3 other c atoms - arranged in a hexagon
trigonal planar

33
Q

What are the properties of graphite?

A

layers can slide - weak d-d forces
high MP = covalent bonds need to be broken
delocalised electrons move freely within a layer = conducts electricity

34
Q

What are graphite’s uses?

A

lubricants
pencils

35
Q

Describe the structure of graphene?

A

iduvidual layers of hexagonal rings of 6 c atoms
each c atom is bonded to 3 other c atoms
trigonal planar

36
Q

What are the properties of graphene?

A

high tensile strength
very high electrical conductivity
high MP

37
Q

What are the uses of graphene?

A

biomedicene - drug delivery
electronics
membranes for cleaning water

38
Q

What bonding type is found in groups 1-3?

A

giant metallic

39
Q

What bonding types are found in groups 4-7?

A

giant covalent

40
Q

What bonding type is found in group 8?

A

simple molecular

41
Q

Why is the melting point of Be higher than Li?

A

Be has more outer shell electrons therefore more delocalised electrons per atom = metallic bonding is stronger

42
Q

Why does carbon have a higher Mp than Boron?

A

C has 4 covalent bonds per atom
B only has 3 covalent bonds per atom
more energy needed in C

43
Q

Why do N,O,F and Ne have low MP?

A

they are simple molecular
only london forces need to be broken

44
Q

Why does neon have a lower MP and BP than N,O and F?

A

the other simple molecular elements are diatomic
neon exists as induvidual atoms - fewer electrons and smaller SA for contact with other atoms
fewer and weaker london forces

Chemisty A level (28 decks)

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