AQA GCSE Combined Science: Trilogy Chemistry Paper 1 (Foundation), 2020: Question 5

11 marks · Standard Demand difficulty · Short Answer

Answer questions about the periodic table, including early ordering by atomic weight, Mendeleev’s placement of iodine, melting points of Group 1 metals, electron transfer in lithium chloride, and why potassium is more reactive than lithium.

Practise this question

Question

The page contains a set of five sub-questions about elements in the periodic table. Part 05.1 asks which property was used to arrange elements in early periodic tables, with tick boxes for atomic number, atomic weight, and mass number. Part 05.2 gives a small section of Mendeleev’s periodic table with iodine, tellurium, bromine, chlorine, selenium, sulfur, barium, and tellurium-related values, asking why iodine was placed in the shown column. Part 05.3 shows Table 3 with melting points of lithium, sodium, and potassium, and asks what state lithium is at 100 °C with choices gas, liquid, or solid. Part 05.4 asks the student to complete a bar chart in Figure 8 using the melting points of the Group 1 metals, with lithium already plotted and blank bars for sodium and potassium. Part 05.5 shows dot-and-cross diagrams of lithium and chlorine reacting to form lithium chloride and asks what happens to the atoms’ electrons. Part 05.6 shows electronic structures of lithium and potassium atoms and asks for two reasons why potassium is more reactive than lithium.
Question text

05 This question is about elements in the periodic table.

05.1 What property was used to arrange elements in early periodic tables?

[1 mark]

Tick ( ) one box.

Atomic number

Atomic weight

Mass number

05.2 In early periodic tables, iodine (I) was placed before tellurium (Te).

Mendeleev placed iodine after tellurium.

Figure 7 shows part of Mendeleev’s periodic table.

Figure 7

Suggest one reason why Mendeleev placed iodine in the column shown

in Figure 7.

[1 mark]

Table 3 shows the melting points of three Group 1 metals.

Table 3

Metal Melting point in °C

Lithium 180

Sodium 98

*15* Potassium 63

05.3 What state is lithium at 100 °C?

Use Table 3.

[1 mark]

Tick ( ) one box.

Gas Liquid Solid

05.4 Complete the graph in Figure 8.

Use Table 3.

You should:

• complete the scale on the y-axis

• draw bars to show the melting points of sodium and potassium.17

[3 marks]

Figure 8

05.5 Lithium reacts with chlorine to produce lithium chloride.

Figure 9 shows what happens to the electrons in the outer shells when a lithium atom

reacts with a chlorine atom.

The dots (o) and crosses (x) represent electrons.

*17* Figure 9

Describe what happens to a lithium atom and to a chlorine atom when they react.

Use Figure 9 to answer in terms of electrons.

[3 marks]

05.6 Lithium and potassium are in the same group of the periodic table.

Figure 10 represents the electronic structures of a lithium atom and of a

potassium atom.

Figure 10

*18* Give two reasons why potassium is more reactive than lithium.

[2 marks]

Mark scheme

Show the mark scheme The mark scheme lists one mark for answering 'atomic weight' in 05.1. For 05.2 it accepts that iodine was placed there because the properties were similar, especially similar properties to halogens such as bromine, chlorine, or fluorine. For 05.3 it gives 'solid'. For 05.4 it requires the y-axis scale to reach 180, a bar at 98 °C for sodium, and a bar at 63 °C for potassium. For 05.5 it awards marks for lithium losing one electron, chlorine gaining one electron, and either ions being formed, lithium becoming positive, chlorine becoming negative, or full outer shells/noble gas structure forming. For 05.6 it awards two marks for any two explanations such as reactivity increasing down the group, potassium having more shells, its outer electron being further from the nucleus, more shielding, or weaker attraction between nucleus and outer electron. The total shown is 11 marks.

AO /

Question Answers Extra information Mark

Spec. Ref.

05.1 atomic weight 1 AO1

5.1.2.2

05.2 (because) properties were 1 AO3

similar 5.1.2.2

or

(because) iodine has similar / allow symbols

same properties as bromine /

chlorine / fluorine

05.3 solid 1 AO3

5.1.2.5

5.2.2.1

05.4 scale on the y-axis up to 180 ignore scale beyond 180 1 AO2

5.1.2.4

5.2.2.1

bar for sodium at 98 (oC) allow a tolerance of ± half a 1

small square

bar for potassium at 63 (oC) allow a tolerance of ± half a 1

small square

05.5 max 2 marks if reference to

incorrect particle / bonding

lithium (atom) loses one electron 1 AO2

chlorine (atom) gains one 1 AO2

electron

any one from: 1 AO1

• ions are formed allow ionic bonding

• lithium forms positive ion 5.1.2.3

• chlorine forms negative ion 5.2.1.2

• form a full outer shell(s) /

level(s)

allow noble gas structure is

formed

05.6 allow energy levels for shells

allow converse for lithium

any two from: 2 AO1

AO2

• reactivity of elements 5.1.2.3

increases going down the 5.1.2.5

group

• potassium has more shells

• potassium can lose an (outer)

electron more easily

• potassium has an outer shell /

electron further away from the

nucleus

• potassium has more shielding

(of the outer shell / electron)

• potassium has a weaker

attraction between nucleus

and outer shell / electron

Total 11

How to answer it

Periodic Table and Reactivity Study Guide

What this question tests:

This question assesses your understanding of the development of the periodic table, physical properties of Group 1 metals, ionic bonding (electron transfer), and the trends in reactivity for Group 1 elements.

05.1 & 05.2: Early Periodic Tables

✅ Correct Answers

05.1: Atomic weight.

05.2: Iodine has similar chemical properties to the other elements in that column (fluorine, chlorine, bromine).

💡 Key Knowledge

Early chemists like Mendeleev arranged elements by atomic weight. However, he famously left gaps and swapped elements (like Te and I) to ensure elements with similar properties stayed in the same vertical group.

05.3 & 05.4: Group 1 Physical Properties

✅ Correct Answer (05.3)

Solid. Since the melting point of lithium is 180 °C, at 100 °C it is still below its melting point.

🧠 Exam Technique (05.4)

When completing a graph:

  • Scale: Ensure your y-axis goes up to at least 180.
  • Precision: Use a sharp pencil. For 98 °C, draw the bar just below the 100 line. For 63 °C, place the top of the bar slightly above the 60 line.

05.5: Ionic Bonding

✅ Correct Answer

1. Lithium atom loses one electron.

2. Chlorine atom gains one electron.

3. Ions are formed (or a full outer shell is achieved).

❌ Common Errors

Do not say "the atoms share electrons"—that is covalent bonding. For ionic bonding, always focus on the transfer of electrons.

05.6: Trends in Reactivity

💡 Key Knowledge: Why Potassium is more reactive

Reactivity increases as you go down Group 1 because:

  • Potassium has more electron shells than lithium.
  • The outer electron is further from the nucleus.
  • There is more shielding from inner shells.
  • There is a weaker electrostatic attraction between the nucleus and the outer electron, making it easier to lose.

🧠 Exam Technique

To get both marks, you must link the structure (more shells/shielding) to the effect (weaker attraction/easier to lose electron). Don't just list facts; explain the consequence!

Topics

Chemistry · C1: Atomic Structure and the Periodic Table · C2: Bonding, Structure and the Properties of Matter

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Chemistry Paper 1 (Foundation), 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.