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AS Chemistry > 3.1.1 - Periodicity > Flashcards

3.1.1 - Periodicity Flashcards

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1
Q

What do metal elements exist as?

A

Giant metallic lattice structures.

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2
Q

Which electrons are delocalised in metallic structures?

A

The electrons in the outermost shell of a metal element.

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3
Q

What are electrons in metals able to do?

A

Free to move about the metal.

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4
Q

What do positive cations do?

A

Occupy fixed positions in a giant lattice.

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5
Q

How are metals held together and therefore what is metallic bonding?

A

The strong electrostatic attraction between positive ions and delocalised electrons.

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6
Q

What affects the melting point of a metal?

A

The number of delocalised electrons per atom. The ionic radius, as a smaller one will hold the delocalised electrons closer to the nucleus.

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7
Q

Why are mp and bp high in a metal?

A

Attractions between ions and electrons are strong, therefore a large amount of energy is required to dislodge ions.

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8
Q

Why can metals conduct?

A

Delocalised electrons are free to move throughout the lattice and can carry a charge.

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9
Q

Why are metals malleable and ductile?

A

As no bonds holding specific ions together, the metal ions can slide past each other when the structure is pulled, so metals are malleable and ductile.

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10
Q

Why are metals insoluble?

A

The strength of the metallic bond is too great for any solvent to overcome.

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11
Q

What are giant covalent lattices?

A

Huge networks of covalently bonded atoms.

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12
Q

Why can carbon atoms form giant covalent lattices?

A

Because they can each form four strong, covalent bonds.

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13
Q

What are allotropes?

A

Different forms of the same element in the same state.

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14
Q

What are examples of carbons allotropes?

A

Diamond, graphite and graphene.

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15
Q

Why do giant covalent lattices have high mp and bp?

A

Large amounts of energy are needed to break the bonds between the atoms.

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16
Q

Why don’t giant covalent lattices conduct electricity?

A

No free electrons that are able to carry a charge.

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17
Q

How are the atoms arranged in diamond?

A

Each carbon atom has four strong covalent bonds to other carbon atoms. They are arranged in a tetrahedral shape.

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18
Q

Why does diamond have strong mp and bp?

A

Strong covalent bonds which require large amounts of energy to break.

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19
Q

As diamond is hard what is it used in?

A

Diamond drill tips and saws.

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20
Q

Why is diamond a good thermal conductor?

A

Vibrations can travel easily through the stiff lattice.

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21
Q

Why won’t diamond conduct electricity?

A

All outer electrons are held in localised bonds.

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22
Q

Is diamond soluble?

A

No.

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23
Q

How are carbon atoms arranged in graphite?

A

Each carbon atom is covalently bonded to three other carbon atoms and these are arranged in layers. This leaves one electron per carbon between the layers.

24
Q

Why can graphite conduct electricity?

A

Delocalised electrons throughout structure can conduct electricity.

25
Q

Why can sheets in graphite slide over each other?

A

Weak forces between layers.

26
Q

Why can graphite be used to make strong, lightweight sports equipment?

A

Layers are quite far apart compared to the length of the covalent bonds, so graphite is less dense.

27
Q

Why does graphite have a high melting point?

A

Strong covalent bonds in the hexagonal sheets.

28
Q

Why is graphite insoluble?

A

Covalent bonds in the sheets are too strong to break.

29
Q

What are the sheets in graphite bonded by?

A

Weak London forces.

30
Q

What is graphene?

A

A sheet of carbon atoms joined together in hexagons. The sheet is just one atoms thick, making it a two dimensional compound.

31
Q

Why is graphene the best known conductor?

A

Delocalised electrons are free to move along the sheet. Without layers, they can move quickly above and below the sheet.

32
Q

Why is graphene strong?

A

The delocalised electrons strengthen the covalent bonds between the carbon atoms.

33
Q

What are the properties of a single layer of graphene?

A

Transparent and incredibly light.

34
Q

What properties of graphene make it good for high-speed electronics and aircraft technology?

A

High strength, low mass, and good electrical conductivity.

35
Q

What properties of graphene make it good for touch screens on smart phones?

A

Flexible and transparent.

36
Q

What kind of structures do simple covalent molecules have?

A

Simple molecular lattices.

37
Q

How are simple covalent molecules bonded?

A

Weak London forces between molecules, but strong covalent bonds.

38
Q

Why do simple covalent molecules have low mp and bp?

A

They require little energy to break as only intermolecular forces are broken.

39
Q

Why do simple covalent molecules not conduct electricity?

A

No free electrons are able to conduct charge.

40
Q

Are simple covalent molecules soluble?

A

Not in water but are in non-polar substances such as cyclohexane.

41
Q

What is the first ionisation energy?

A

The energy needed to remove one mole of electrons from one mole of gaseous atoms.

42
Q

Write the equation for the 1st ionisation of oxygen.

A

O(g) -> O^+(g) + e-

43
Q

What three factors affect ionisation energy?

A

Nuclear charge, atomic radius, electron shielding.

44
Q

How does nuclear charge affect ionisation energy?

A

The more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons.

45
Q

How does atomic radius affect ionisation energy?

A

An electron close to the nucleus will be much more strongly attracted than one further away.

46
Q

How does electron shielding affect ionisation energy?

A

Inner shell electrons repel the outer shell electrons. The more inner shells the greater the shielding effect and the less attractive force experienced by the outer electrons.

47
Q

What does shielding do?

A

Reduces the net attractive force from the positive nucleus on the outer shell electrons.

48
Q

What happens to ionisation energy as you go down the group>

A

It decreases.

49
Q

Why does ionisation energy decrease as you go down the group?

A

Elements have extra electron shells which results in a larger atomic radius, therefore electrons are further away from the nucleus, reducing their attraction to the nucleus. The extra inner shells shield the outer electrons from the attraction of the nucleus.

50
Q

What does high ionisation energy result in?

A

Strong interaction between the electrons and the nucleus, so more energy is needed to overcome the attraction and remove the electrons.

51
Q

What groups are an exception in the trends in ionisation energies?

A

Between groups 2 and 3, and between groups 5 and 6.

52
Q

Why is there a drop in ionisation energy between groups 2 and 3?

A

The outer electrons in group 3 are in a p orbital which have a slightly higher energy level than s orbitals, so is found further from the nucleus. There is also increased shielding provided by the s orbitals. Therefore increased nuclear charge resulting in ionisation energy dropping slightly.

53
Q

Why is there a drop in ionisation energy between groups 5 and 6?

A

In group 5 elements, the electron is being removed from a singly-occupied orbital, whereas group 6 contain an orbital with 2 electrons. The repulsion between the two electrons means that electrons are easier to remove.

54
Q

Within each shell why do successive ionisation energies increase?

A

Electrons are being removed from increasingly positive ions, and there’s als less repulsion amongst the remaining electrons, so electrons are held more strongly by the nucleus.

55
Q

When does the big jump in ionisation energy occur?

A

When a new shell is broken into as an electron is being removed from a shell closer to the nucleus.

AS Chemistry (24 decks)

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