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OCR AS (A-level) Chemistry > Module 3 Periodic Table and Energy > Flashcards

Module 3 Periodic Table and Energy Flashcards

1
Q

What is the periodic table as a result of

A

Work to order the chemical elements to show patterns of chemical and physical properties

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2
Q

Horizontal rows of elements

A

Periods

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3
Q

Vertical rows of elements

A

Groups

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4
Q

How are elements arranged in the periodic table?

A

In order of increasing atomic number

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5
Q

Defintion of periodicity

A

Repeating patterns of trends across different periods

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6
Q

Why do elements in a group have similar chemical and physical properties?

A

Because they all have the same number of outer electrons

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7
Q

There’s a ___________ ________ from metal to non-metal across each period

A

Periodic trend

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8
Q

True or false: Metals are good conductors of electricity

A

True

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9
Q

True or false: Non-metals are good conductors of electricity

A

False

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10
Q

True or false: Metalloids are non-conductors of electricity

A

False - they are poor conductors of electricity

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11
Q

Chemical reaction always involve the __________ _______

A

Outer shell

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12
Q

Elements in the same period contain a _________________ ________ of electrons

A

Common core

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13
Q

Explain why magnesium is an S-block element (1)

A

S-block elements have their highest energy outer-shell electron in an S-orbital

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14
Q

Explain trends in atomic radii across a period

A

• Protons added to nucleus so nuclear charge increases
• Electrons added to the same shell
• Nuclear attraction on outer shell electrons increases across a period
• Electron shells are drawn inwards by nucleus, making atoms smaller

Trend is: atomic radii decreases across a period from left to right

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15
Q

Explain trends in atomic radii down a group

A

• Number of shells increases
• Outer electron is added to a new shell which is further away from nucleus
• The shielding effect by inner shell electrons increases down a group
• The increase in distance far outweighs the increase in nuclear charge
• The nuclear attraction decreases down a group

Trend is: atomic radii increases down a group

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16
Q

Giant substances have _____________ bonds, so _________ melting and boiling points

A
  1. Strong
  2. High
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17
Q

Simple substances have ___________ bonds, so have ______ melting and boiling points

A
  1. Weak
  2. Low
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18
Q

Describe the melting and boiling points across all the periods in the periodic table

A
  1. Increase gradually between groups 1 and 4 (metallic bonding)
  2. Decrease sharply between groups 4 and 5 (simple covalent)
  3. Are comparatively low between groups 5 and 8 (simple covalent)
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19
Q

What does ionisation energy produce, and how does it achieve this?

A

Produces ions with a positive charge by removing electron from outer shell

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20
Q

What is ionisation energy?

A

Energy required to overcome the ES force

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21
Q

Definition of first ionisation energy

A

The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

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22
Q

Write the first ionisation energy of oxygen

A

O(g) ——> O+(g) + e-

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23
Q

Which 3 factors affect first ionisation energy?

A
  1. Nuclear charge
  2. Distance of outermost electron from nucleus
  3. Electron shielding
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24
Q

Explain how nuclear charge affects first ionisation energy

A

• More protons = higher nuclear charge
• Stronger nuclear attraction on outer electrons
• More energy needed to overcome attraction between nucleus and outer electron

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25
Q

Explain how the distance from the outermost electron affects first ionisation energy

A

• As distance increases, attraction decreases
• Weak nuclear attraction requires less energy to overcome

26
Q

Explain how electron shielding affects first ionisation energy

A

• Shielding effect reduces net nuclear attraction
• More inner shells, more shielding effect, so weaker nuclear attraction

27
Q

What is the shielding effect?

A

Repulsion from electrons in the inner shell

28
Q

Explain whether sodium or lithium has a higher first ionisation energy

A

• As you go down a group number of shells increases
• Electrons added to new shell
• Repulsion of inner shells increases
• Increase in distance far outweighs increase in nuclear charge
• Attraction down a group decreases because atomic radii increases
• (So) lithium has a higher ionisation energy (energy needed to remove it’s outermost electron)

29
Q

Explain the ‘dip’ in ionisation energies of beryllium and boron, and, magnesium and aluminium

A

The explanation is exactly the same for both, below is example of boron and beryllium
Be = 1s2 2s2
B = 1s2 2s2 2p1
• Boron has lower IE than beryllium
• The 2p sub shell in B has a higher energy than the 2s sub-shell
• The 2p1 electron in B needs less energy to be removed, giving boron a lower first ionisation energy

30
Q

Explain the ‘dips’ in ionisation energies for phosphorus and sulphur, and nitrogen and oxygen

A

The explanation is exactly the same for both, below is example of nitrogen and oxygen
N = 1s2 2s2 2p3
O = 1s2 2s2 2p4
• Oxygen has lower IE because in nitrogen, each p orbital contains 1 electron, in oxygen, one p orbital contains 2 electrons paired
• The paired 2p electrons repel each other, meaning it’s easier to remove one electron
• Less energy needed to remove 2p electron from O than N

31
Q

Which elements see ‘dips’ in ionisation energies in period 2?

A

Boron and oxygen

32
Q

Which elements see ‘dips’ in ionisation energies in period 3?

A

Aluminium and sulphur

33
Q

Definition of second ionisation energy

A

Energy required to remove one electron from each 1+ ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

34
Q

Write the second ionisation energy of fluorine

A

F+(g) ——> F2+(g) + e-

35
Q

Explain the ‘one before rule’ when working with ionisation energies

A

The element on the right will be the number of the ionisation energy, e.g., if it’s second, it will be 2, then the element on the left will be the one before.

36
Q

Write the 8th ionisation energy of fluorine

A

F7+(g) ——> F8+(g) + e-

37
Q

How many ionisation energies are possible for boron?

A

This is the number of electrons in a boron atom = 5

38
Q

What do successive ionisation energy graphs provide evidence for?

A

Shells

39
Q

When drawing successive ionisation graphs, what is the first step?

A

Draw out the electron configuration using Neils Bohr’s model

40
Q

Ionisation number

A

The electron, e.g., the 1st ionisation number is the first outer electron removed

41
Q

Explain hwy successive ionisation energies increase with ionisation number?

A

• Once electrons removed, there are fewer electrons, but more protons
• Proton : electron ratio increasses
• Remaining electrons more strongly attracted to nucleus
• More energy needed to remove each electron

42
Q

Why is there a large increase in ionisation energy at a certain point on a successive ionisation graph?

A

Electrons from the next shell are being removed - these have a stronger nuclear attraction

43
Q

Why are all group 2 elements S block elements?

A

Highest energy orbital occupies an S sub shell

44
Q

Why are group 2 metals known as alkaline earth metals?

A

They all form hydroxides which are alkaline

45
Q

What type of structures are group 2 metals?

A

Giant metallic lattice

46
Q

Why are group 2 metals good reducing agents?

A

They undergo oxidation

47
Q

Why does the first ionisation energy decrease down group 2?

A

• Atomic radius increases - more shells
• Greater shielding effect
• Increase in distance far outweighs increase in nuclear charge
• Nuclear attraction on outer shell decreases, so less energy needed to remove an electron.

48
Q

The following data shows the first eight successive ionisation energies of an element.

  1. 590
  2. 1145
  3. 4912
  4. 6474
  5. 8144
  6. 10 496
  7. 12 320
  8. 14 207

In which group might this element be found?

Use data to justify your choice (3)

A
  • Group 2
  • Large increase between second and third ionisation energy
  • 3rd electron in a shell closer to the nucleus
49
Q

General equation for the reaction of group 2 metals and compounds with oxygen

A

Redox equation…

Metal + oxygen —> metal oxide

50
Q

What observations can be made when a group 2 metal or compound reacts with oxygen?

A

Coloured flame e.g., Mg burns with a bright white flame

51
Q

General equation for the reaction of group 2 metals and compounds with water at room temperature

A

Redox…

Metal + water —> metal hydroxide + hydrogen

52
Q

What observations can be made when a group 2 metal or compound reacts with water at room temperature

A
  • Metal hydroxide typically pH 10-12 (strong base)
  • Solid disappears
  • Bubbles of hydrogen gas
  • Very slow reaction
53
Q

General equation for the reaction of group 2 metals and compounds with steam

A

Redox…

Metal + steam —> metal oxide + hydrogen

54
Q

What observations can be made when a group 2 metal or compound reacts with steam?

A

Vigorous reaction compared to room temperature water

55
Q

General equation for the reaction of group 2 metals and compounds with acid

A

Redox…

Metal + acid —> salt + water

(MASH)

56
Q

What observations can be made when a group 2 metal or compound reacts with an acid?

A

Hydrogen is a reducing agent

57
Q

State the trend in reactivity down group 2

A

Increases

58
Q

State the trends in solubility down group 2

A

• Solubility of metal hydroxides in water increases, so, solutions more alkaline
• Solubility of metal sulphates in water decreases
• Solubility of metals increase

59
Q

Explain why Ba(OH)2(aq) has a greater pH than Ca(OH)2(aq) (3)

A
  1. Barium hydroxide more soluble
  2. More OH- ions released in solution
  3. As concentration of OH- ions increases, alkalinity increases
60
Q

Explain to uses of group 2 hydroxides and the reason they’re used (2)

A
  1. Magnesium hydroxide used in indigestion tables as an antacid - neutralises excess stomach acid safely as it is a mild alkali
  2. Calcium hydroxide used in agriculture to neutralise acid soil - neutralises acid soil by reacting with acid substances in soil
61
Q

Explain the use of a group 2 sulphate and the reason why it’s used (1)

A

Barium sulphate used in visualising X rays - insoluble in solution so doesn’t release toxic barium ions into patients bloodstream

OCR AS (A-level) Chemistry (4 decks)

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