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AS chemistry > Unit 1-5 > Flashcards

Unit 1-5 Flashcards

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1
Q

How are ionic crystals held together?

A

Strong electrostatic forces between oppositely charged ions

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2
Q

What is electric neutrality?

A

No overall charge

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3
Q

What is the coordination number?

A

The number of oppositely charged ions which surround an ion

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4
Q

Describe the structure of sodium chloride

A

Giant ionic lattice of Na+ cations and Cl- anions
Coordination number of 6:6
Each ion is surrounded by 6 of the oppositely charged ion
Na+ ions cant fit many Cl- ions around it due to a low number of shells

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5
Q

Describe the structure of caesium chloride

A

Giant ionic lattice made of Cs+ cations and Cl- anions
Coordination number of 8:8
Each ion is surrounded by 8 of the oppositely charged ion
Cs+ ions can fit many Cl- ions around it due to a large number of shells

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6
Q

What is metallic bonding?

A

The attraction between positive cations and a sea of negative delocalised electrons
The electrons move around both the ion they belong to and nearby ions

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7
Q

Why is the metal lattice built of cations?

A

Because while electrons don’t leave the structure they do leave the atom

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8
Q

Why does an increase in the number of electrons in the outer shell strengthen metallic bonding?

A

Cations increase in positivity
The number of delocalised electrons increases

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9
Q

Why do metals have high melting temperatures?

A

Strong attraction between the positive ions and sea of delocalised e-

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10
Q

Why are metals electrolytes

A

Electrons are free to move and carry electrical energy when potential difference is applied

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11
Q

Why are metals malleable and ductile?

A

Layers of metal ions can slide past each other since the sea of delocalised e- move to maintain metallic bonding

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12
Q

Why are metals hard and strong?

A

Strong metallic bonds require large amounts of energy to separate the cations and sea of delocalised e-

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13
Q

When covalent bonding extends indefinitely, what determines bonds per atom and direction of bonds?

A

Bonds per atom and direction of bonds are the same as that of the molecule

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14
Q

Unit 1.5

What is an allotrope?

A

Same element with a different arrangement of atoms within the structure

Diamond and graphite are allotropes of carbon

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15
Q

Unit 1.5

What is the structure of diamond?

A

Tetrahedral structure
Bond angle of 109.5°
Coordination number of 4

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16
Q

Unit 1.5

What is the structure of graphite?

A

Hexagonal arrangement
Bond angle of 120°
Coordination number of 3

Layers of carbon

17
Q

Unit 1.5

What holds the layers of graphite together?

A

Van-der-waals bonds

Weak bonds allow the layers to slide over eachother

18
Q

Unit 1.5

Describe the strength of diamond

A

Very hard due to strong covalent bonds creating a rigid structure

19
Q

Unit 1.5

Describe the strength of graphite

A

Soft due to weak VDW forces between layers

20
Q

Unit 1.5

Describe the conductivity of diamond

A

Does not conduct electricity as each carbon is bonded to 4 others, resulting in no free electrons

21
Q

Unit 1.5

Describe the conductivity of graphite

A

Does conduct electricity as each carbon is only bonded to 3 others, meaning there’s one free electron per atom of carbon

22
Q

Unit 1.5

Describe the melting point of diamond and graphite

A

Very high due to strong covalent bonds between carbon atoms

Graphites melting point is higher

23
Q

Unit 1.5

What is the density of diamond?

A

High density of 3.53g/cm3

C-C hold atoms closely per unit of volume

24
Q

Unit 1.5

What is the density of graphite?

A

Low density of 2.25g/cm3

VDW bonds hold atoms far away

25
Q

Unit 1.5

Describe the solubility of diamond and graphite

A

Insoluble
Covalent bonds are so strong the atoms cannot be separated by the solvent

26
Q

Unit 1.5

What is the range of sizes for nanoparticles?

A

1-100 nanometers (nm)

27
Q

Unit 1.5

What are fullerenes?

A

Nanoparticles of carbon shaped as hollow spheres or closed tubes

28
Q

Unit 1.5

Why do fullerenes have a high melting point?

A

Strong covalent bonds

29
Q

Unit 1.5

Why are fullerenes conductive?

A

1 free electron per carbon atom

30
Q

Unit 1.5

What is a buckminster?

A

The smallest fullerene (C60)
Shaped as a hollow sphere

Used as cages to administer drugs into the body

31
Q

Unit 1.5

What are carbon nanotubes?

A

Cylindrical fullerenes consisting of hexagons of carbon

32
Q

Unit 1.5

What are the properties of carbon nanotubes?

A

Very high tensile strength
Unique electrical properties
Good heat conductance
Large surface area
Metal atoms can be attached to the outside

33
Q

Unit 1.5

What are the uses of carbon nanotubes

A

Used for semiconductors in electronic circuits
Often used to reinforce various objects, such as tennis racket frames and golf club shafts
Used as a platform for industrial catalysts due to large surface area

34
Q

Unit 1.5

What are multiwalled nanotubes?

A

Several tubes rotate and slide within each other with almost no friction

35
Q

Unit 1.5

What are D-molecular crystals?

A

Discrete molecules bonded by strong intermolecular VDW bonds

Stronger intramolecular covalent bonds between atoms

36
Q

Unit 1.5

Why do I2 crystals have a higher melting point than Cl2 crystals?

A

The strength of VDW forces increase with molecular size

37
Q

Unit 1.5

What are the general properties of D-molecular crystals?

A

Soft
Low melting and boiling point
Do not conduct electricity as solid or liquid (don’t exist as gases)
Soluble in polar solvelnts (H2O)
Insoluble in non-polar solvents (tetrachloromethane)

38
Q

Unit 1.5

Why are D-molecular crystals insoluble in polar solvents?

A

VDW forces are not strong enough to break the up the H-bonding between polar molecules

39
Q

Unit 1.5

What is the structure of ice?

A

Liquid H2O is tetrahedral and has H bonds bustween neighbouring O and H atoms

AS chemistry (7 decks)

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