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Chemistry Unit 1 🤍 > 1.6 The periodic table > Flashcards

1.6 The periodic table Flashcards

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1
Q

How are elements arranged in the periodic table?

A

Elements are arranged in order of increasing atomic number. They are positioned in vertical groups and horizontal periods.

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2
Q

In terms of subshells, how is the periodic table divided up?

A

Divided into s, p, d and f blocks.

The block denotes the subshell the elements’ valence electrons are in.

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3
Q

What does the group and period of an element show?

A

Period - tells you how many electron shells the atom has.

Group - tells you how many electrons are in the atom’s outer shell.

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4
Q

Define oxidation in terms of electron transfer

A

Oxidation is the loss of electrons. (OIL)

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5
Q

Define reduction in terms of electron transfer

A

Reduction is the gain of electrons. (RIG)

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6
Q

What is the general trend in first ionisation energy across Period 2 and Period 3?

A

As you go along the period, first ionisation energy increases.

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7
Q

Explain the reason for the drop in ionisation energy between nitrogen and oxygen in Period 2

A

The electron being removed from oxygen is in an electron pair so the electron is removed more easily due to repulsion between the two electrons.

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8
Q

Explain the reason for the drop in ionisation energy between magnesium and aluminium in Period 3

A

The electron being removed from aluminium is in the 3p orbital rather than the 3s orbital.

The 3p orbital is at a slightly higher energy level and the electron is found further from the nucleus.

Aluminium has a lower ionisation energy as the electron is less attracted to the nucleus due to the increased distance and shielding from the 3s orbital.

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9
Q

Why does first ionisation energy increase across a period?

A

First ionisation energy increases across a period because the number of protons is increasing whilst the atomic radius is decreasing.

This means there is a higher nuclear charge attracting the outer electrons.

There is not much change in shielding across the period so this does not have a significant effect.

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10
Q

Explain the trend in ionisation energy down a group in the periodic table

A

lonisation energy decreases down the group.

This is because the amount of shielding increases along with atomic radius, so the outer electron is attracted more weakly to the nucleus, making it easier to remove.

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11
Q

What is the trend in electronegativity across a period?

A

As you go across a period, the electronegativity increases.

This is because there are more protons and decreasing atomic radius so there is an increasing nuclear attraction to the electron density.

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12
Q

What is the trend in electronegativity down a group?

A

As you go down a group, the electronegativity decreases. This is because electron shielding and atomic radius increases so the nuclear attraction to the bonding pair weakens.

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13
Q

How do Group 2 elements react with oxygen?

A

2X + O₂ → 2XO
Where X is the Group 2 element.

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14
Q

How do Group 2 elements react with water?

A

X + 2H₂O → X(OH)₂ + H₂
Where X is the Group 2 element.

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15
Q

What is the chemical equation for the reaction between calcium and water?

A

Ca + 2H₂O → Ca(OH)₂ + H₂

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16
Q

What is the chemical equation for the reaction between strontium and oxygen?

A

2Sr + O₂ → 2SrO

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17
Q

What is the chemical equation for the reaction between magnesium chloride and sodium carbonate?

A

MgCl₂ + Na₂ CO₃ → MgCO₃ + 2NaCl

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18
Q

What is the chemical formula of the compound formed when barium ions react with sulfate ions?

A

Barium ions → Ba²⁺
Sulfate ions → SO₄² ⁻
Barium sulfate: BaSO₄

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19
Q

Describe how you would carry out a flame test

A
  • Clean a nichrome wire using hydrochloric acid.
  • Turn the Bunsen burner onto the blue flame.
  • Dip the wire in a solution of the substance being tested.
  • Place the wire in the flame and record the flame colour.
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20
Q

What colour is observed in the flame test for lithium ions?

A

Crimson flame

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21
Q

What colour is observed in the flame test for sodium ions?

A

Yellow flame

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22
Q

What colour is observed in the flame test for potassium ions?

A

Lilac flame

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23
Q

What colour is observed in the flame test for calcium ions?

A

Orange-red flame

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24
Q

What colour is observed in the flame test for strontium ions?

A

Red flame

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25
Q

Why must the wire be cleaned before carrying out a flame test?

A

To remove any unwanted ions that might obscure the colour of the flame.

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26
Q

Why can a flame test not be used when a compound contains a mixture of metal ions?

A

The flame colours of the ions will blend together so the individual flame colours won’t be seen and the ions can’t be identified.

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27
Q

Explain the trend in reactivity down Group 1 from lithium to potassium

A

In order to react, Group 1 elements lose an electron to form a 1+ ion.

Down Group 1, the atomic radius and shielding increases so the outer electron is lost more easily.

This means reactivity increases down Group 1.

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28
Q

Explain the trend in reactivity down Group 2 from magnesium to barium

A

In order to react, Group 2 elements lose two electrons to form 2+ ions.

Down Group 2, the atomic radius and shielding increases so the outer electrons are lost more easily.

This means reactivity increases down Group 2.

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29
Q

What is the trend in thermal stabilities of Group 1 and 2 carbonates?

A

The thermal stabilities of Group 1 and 2 carbonates increase down the groups.

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30
Q

What is the trend in thermal stabilities of Group 1 and 2 nitrates?

A

The thermal stabilities of Group 1 and 2 nitrates increase down the groups.

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31
Q

Why do the thermal stabilities of carbonates and nitrates increase down Groups 1 and 2?

A

Down the groups, the ionic radii increases whilst the magnitude of charge remains the same.

Therefore the charge densities of the Group 1 and 2 ions decrease.

As the ions have a lower charge density, they distort the CO₃²⁻
and NO₃⁻ ions less, so the compounds take more energy to breakdown.

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32
Q

What is the trend in solubility of Group 2 hydroxides down the group?

A

The solubility of Group 2 hydroxides increases down the group.

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33
Q

What is the trend in solubility of Group 2 sulfates down the group?

A

The solubility of Group 2 sulfates decreases down the group.

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34
Q

What is produced when a Group 1 or Group 2 hydroxide reacts with a dilute acid?

A

Salt and water

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35
Q

What is the chemical equation for the reaction between sodium hydroxide and dilute hydrochloric acid?

A

NaOH + HCl → NaCl+ H₂O

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36
Q

What is produced when a Group 1 or Group 2 oxide reacts with a dilute acid?

A

Salt and water

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37
Q

What is the chemical equation for the reaction between lithium oxide and dilute sulfuric acid?

A

Li₂O+ H₂SO₄ → Li₂SO₄ + H₂O

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38
Q

What are the Group 7 elements often referred to as?

A

The halogens

39
Q

Why do the halogens exist in different states at room temperature? What is the trend down the group?

A

At room temperature, chlorine is gaseous, bromine is liquid and iodine is solid because they have different melting and boiling points. As you go down the group, melting and boiling point increases.

40
Q

Why does melting and boiling point increase down Group 7?

A

The molecules get bigger and the number of electron shells increases down the group.

This means there are more intermolecular forces to overcome during melting/boiling, so more energy is required to change state.

41
Q

What is produced when a halogen reacts with a metal?

A

A salt is produced. E. g.
2Na + Cl₂ → 2NaCl

42
Q

Why does reactivity decrease down Group 7?

A

As you go down Group 7, the outer shell is further from the nucleus and electron shielding increases.

Attraction between the nucleus and outer electrons decreases so it is harder for the atom to gain an electron, meaning reactivity decreases.

43
Q

Link the reactivity trend of the halogens to the relative oxidising power of the halogens

A

Reactivity decreases down Group 7. This means the oxidising power of the halogens also decreases down the group because it is harder for the atom to gain an electron.

44
Q

How can halide ions be identified in a solution?

A

Add nitric acid followed by silver nitrate solution. Silver halide precipitates will form. Ammonia solution can be added to further distinguish between the halide precipitates.

Silver chloride: White precipitate
soluble in dilute ammonia

Silver bromide: Cream precipitate soluble in concentrated ammonia

Silver iodide: Yellow precipitate insoluble in ammonia

45
Q

What is a redox reaction?

A

A redox reaction is one in which oxidation and reduction occur on different species simultaneously.

46
Q

When does a halogen displacement reaction occur?

A

When a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide.

47
Q

Why can iodine not displace chloride or bromide ions from an aqueous ionic solution?

A

Displacement will only occur if iodine is more reactive than the halogen in the ionic compound.

Reactivity decreases down the group and iodine is below chlorine and bromine so no displacement reactions will take place.

48
Q

What is the chemical equation for the reaction between bromine and potassium iodide?

A

Br₂ + 2Kl → I₂ + 2KBr

49
Q

What type of reactions are halogen and halide ion displacement reactions?

A

Redox

50
Q

What is a common use of chloride and fluoride ions?

A

The ions are used in water treatment because they kill bacteria in the water.

51
Q

What are the health and ethical debates surrounding the use of chloride and fluoride ions in water?

A

People argue that, since chlorine is toxic, it shouldn’t be put into water supplies. It is also argued that people should have the choice about whether their water is treated with these ions.

52
Q

What is a precipitation reaction?

A

A reaction in which two soluble salts combine to form an insoluble salt.

53
Q

What is gravimetric analysis?

A

Gravimetric analysis involves a collection of quantitative experimental techniques which are used to determine the mass or concentration of a substance by measuring a change in mass.

54
Q

What chemicals can be used to carry out gravimetric analysis on an unknown metal chloride?

A

0.5 mol dm⁻³ AgNO₃solution
6.0 mol dm⁻³ HNO₃ solution
2.0 mol dm⁻³ HCl solution

55
Q

What are the hazards associated with AgNO₃ , HNO₃ and HCI?

A

AgNO₃ - corrosive
HNO₃ - corrosive
HCl - irritant

56
Q

Outline a method to identify an unknown metal chloride using gravimetric analysis

A
  1. Weigh 0.3 g of the unknown chloride into a 250cm³ beaker.
  2. Dissolve this sample in 100 cm³ of deionised water and add 3 cm³ of 6.0 mol dm⁻³ HNO₃.
  3. Add 20cm³ of AgNO₃ solution until silver chloride forms a gel and then add a further 5cm³ of AgNO₃
  4. Heat the beaker carefully for 10 minutes - do not allow the solution to boil.
  5. Leave the solution to cool for 2 hours.
  6. Weigh a filter paper and place in a filter funnel.
  7. Pour the mixture into the funnel and wash the precipitate into the beaker with 3cm³ of wash solution.
  8. Transfer all the precipitate to the filter funnel and wash with 20cm³ of wash solution.
  9. Test the used wash solution by adding 3 drops of HCl solution. If a precipitate forms, wash with a further 10 cm³ and re-test.
  10. Dry the precipitate in the filter paper at 105 °C until constant mass is attained
57
Q

Identify the filtrate and residue in filtration

A

Filtrate - the solution which passes through the filter paper.
Residue - the solid collected on the filter paper.

58
Q

In the gravimetric analysis of a metal chloride, why is filtration used?

A

Filtration separates the silver chloride precipitate from the solution. The silver chloride is left as the residue on the filter paper.

59
Q

In the gravimetric analysis of a metal chloride, why is the filter paper weighed before use?

A

This measurement can be used to calculate the mass of the solid on the filter paper at the end of the reaction. This means the solid does not have to be scraped off the paper to be weighed, so it gives a more accurate calculation.

60
Q

Why should the solution not be allowed to boil in the gravimetric analysis of a metal chloride?

A

Some of the solution may evaporate, causing some of the product to be lost. This would decrease the expected yield.

61
Q

Why are washings used in the gravimetric analysis of a metal chloride?

A

Washings are used to remove all of the precipitate from the beaker, allowing it to pour through the filter funnel. It collects any solid which may have stuck to the walls of the beaker, ensuring a maximum yield of product.

62
Q

Why is deionised water often used as a wash solution?

A

Deionised water does not have any ions in it so it will not interfere with any reactions taking place.

63
Q

Why is HNO₃ diluted into the wash solution for the gravimetric analysis of an unknown metal chloride?

A

The HNO₃ reacts with any ions which may also produce a white precipitate (e.g. carbonate ions).

This ensures that if a white precipitate is produced, it can be assumed to be silver chloride.

64
Q

In the gravimetric analysis of a metal chloride, why is the used wash solution tested with HCI?

A

The HCl will react with any silver ions (Ag⁺ ions) which have not yet formed silver chloride. The reaction will produce a white precipitate.

65
Q

In the gravimetric analysis of a metal chloride, why is the solution re-filtered if the filtrate produces a white precipitate when tested with HCI?

A

The white precipitate shows that there is still some silver chloride to be collected in the filter paper.

It must be refiltered to ensure the maximum amount of product is collected.

The filtrate must be re-tested with HCl until no precipitate forms.

66
Q

Why is a final filtrate dried in a drying oven until constant mass?

A

The constant mass indicates that all the water has evaporated.

67
Q

Give the ionic equation for the reaction between silver nitrate and the unknown metal chloride

A

Ag⁺ (aq) + Cl⁻ (aq)→ AgCI (s)

68
Q

What causes the white precipitate in the gravimetric analysis of an unknown metal chloride?

A

Silver chloride (AgCl)

69
Q

Why is HNO₃ added to a chloride solution before AgNO₃?

A

The HNO₃ reacts with other ions that might also give a white precipitate with AgNO₃, e.g. carbonate ions.

This prevents the ions from being able to react with the AgNO₃.

70
Q

In the gravimetric analysis of a metal chloride, why is the reaction mixture heated before filtering?

A

The heating causes the silver chloride precipitate particles to start to coagulate (form a gel) which allows it to be filtered more easily.

71
Q

In the gravimetric analysis of a metal chloride, why is the reaction mixture left to stand for two hours?

A

The mixture is left to stand so that the silver chloride fully coagulates after heating.

This will make the sample easier to filter.

72
Q

How do you calculate the mass of the dried solid collected on the filter paper?

A

Mass of solid =
Mass of solid on filter paper - Initial mass of filter paper

73
Q

Given the solutions below, how could you carry out a test to identify them from 6 unlabelled bottles?
Ba(NO₃)₂, Pb(NO₃)₂, MgSO₄, KI, Na₂CO₃, Zn(NO₃)₂

A
  1. Draw out a table to record all observations.
  2. Test 2 cm of each solution with a few drops of each of the other solutions in turn.
  3. Record your observations in the table.
74
Q

What is observed when Ba(NO₃)₂ is added to Pb(NO₃)₂?

A

No reaction observed - solution remains colourless.

75
Q

What is observed when Ba(NO₃)₂ is added to MgSO₄?

A

A white precipitate is produced.

76
Q

What causes the white precipitate in the reaction between Ba(NO₃)₂ and MgSO₄?

A

The sulfate ions.
BaSO₄ is a white precipitate.

77
Q

What is observed when Ba(NO₃)₂ is added to KI?

A

No reaction observed - solution remains colourless.

78
Q

What is observed when Ba(NO₃)₂ is added to Na₂CO₃?

A

A white precipitate produced.

79
Q

What causes the white precipitate in the reaction between Ba(NO₃)₂ and Na₂CO₃?

A

The carbonate ions.
BaCO₃ is a white precipitate.

80
Q

What is observed when Pb(NO₃)₂ is added to MgSO₄?

A

A white precipitate is produced.

81
Q

What causes the white precipitate in the reaction between Pb(NO₃)₂ and MgSO₄?

A

The sulfate ions.
PbSO₄ is a white precipitate.

82
Q

What is observed when Pb(NO₃)₂ is added to KI?

A

A yellow precipitate is produced.

83
Q

What causes the yellow precipitate in the reaction between Pb(NO₃)₂ and KI?

A

The iodide ions.
PbI₂ is a yellow precipitate.

84
Q

What is observed when Pb(NO₃)₂ is added to Na₂CO₃?

A

A white precipitate is produced.

85
Q

What causes the white precipitate in the reaction between Pb(NO₃)₂ and Na₂CO₃?

A

The carbonate ions.
PbCO₃ is a white precipitate.

86
Q

What is observed when MgSO₄ is added to KI?

A

No reaction observed - solution remains colourless.

87
Q

What is observed when MgSO₄ is added to Na₂CO₃?

A

A white precipitate is produced.

88
Q

What causes the white precipitate in the reaction between MgSO₄ and Na₂CO₃?

A

The carbonate ions.
MgCO₃ is a white precipitate.

89
Q

What is observed when MgSO₄ is added to Zn(NO₃)₂?

A

No reaction observed - solution remains colourless.

90
Q

What is observed when Kl is added to Zn(NO₃)₂?

A

No reaction observed - solution remains colourless.

91
Q

What is observed when Kl is added to Na₂CO₃?

A

No reaction observed - solution remains colourless.

92
Q

What is observed when Zn(CO₃)₂ is added to Na₂СО₃?

A

A white precipitate is produced.

93
Q

What causes the white precipitate in the reaction between Zn(CO₃)₂ and Na₂CO₃?

A

The carbonate ions.
Zn(CO₃)₂ is a white precipitate.

94
Q

Why does it not matter exactly how much of each solution is added to the other?

A

It is qualitative analysis which means the exact measurements are not being recorded.

It only matters that enough of the solution is added for a possible reaction to be observed.

Chemistry Unit 1 🤍 (7 decks)

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