Skip to content
Cambridge IGCSE0620

Arrangement of elements

Chemistry 0620 Chapter Notes

What this chapter covers

Arrangement of elementsGroup I propertiesGroup VII propertiesTransition elementsNoble gases
ShareWhatsAppPost
Arrangement of elements notes

Read online free. Download a watermarked copy with a free account.

Read the notes

The full Arrangement of elements notes as text: skim, search, and jump between subtopics.

~30 min read

In this chapter

  1. 1Periods, groups and proton number
  2. 2Metals to non-metals across a period
  3. 3Group number and ion charge
  4. 4Same group, similar properties
  5. 5Predicting from position
  6. 6Trends down a group
  7. 7Group I: the alkali metals
  8. 8Melting point decreases down the group
  9. 9Density increases down the group
  10. 10Reactivity increases down the group
  11. 11The three trends together
  12. 12Predicting a value for another element
  13. 13Predicting a physical state
  14. 14Halogens: diatomic non-metals
  15. 15Trends down the group
  16. 16Appearance at r.t.p.
  17. 17Displacement reactions
  18. 18Explaining displacement
  19. 19Predicting properties
  20. 20High density and high melting point
  21. 21Transition elements as catalysts
  22. 22Coloured compounds
  23. 23Variable oxidation numbers
  24. 24Iron(II) and iron(III)
  25. 25Group VIII: unreactive gases
  26. 26Monatomic, not diatomic
  27. 27Why they are unreactive
  28. 28Helium is the exception to eight

1. Periods, groups and proton number

The Periodic Table arranges the elements in order of increasing proton number (atomic number). The horizontal rows are periods. The vertical columns are groups.

The table is not in order of nucleon number.

Examiner insight

“Distractor D was the most common answer with candidates assuming that the Periodic Table places the elements in order of nucleon number rather than atomic number.”

Worked example 11 mark

Which statements about the Periodic Table are correct?

1 The horizontal rows of the Periodic Table are called groups.

2 The Periodic Table is arranged in order of increasing proton number.

3 The elements in the second column from the left of the Periodic Table form ions with a charge of 2+.

4 Elements in a horizontal row of the Periodic Table become more metallic going from left to right.

A 1 and 2 B 1 and 4 C 2 and 3 D 3 and 4

  1. 1

    Statement 1 is wrong: the horizontal rows are periods.

  2. 2

    Statement 4 is wrong: metallic character decreases from left to right.

  3. 3

    Statements 2 and 3 are correct: C. [1]

2. Metals to non-metals across a period

Going from left to right across a period, the elements change from metals to non-metals. Metallic character decreases.

Across the same period, the number of outer-shell electrons increases.

Examiner insight

“Four out of five of the weaker candidates chose Distractor B or Distractor C which both describe an increase in metallic character.” “Candidates are advised to use the Periodic Table provided to check their answer by referring to the position of elements they know well such as iron or oxygen.”

Worked example 11 mark

Which row describes the changes across a period of the Periodic Table, from left to right?

number of outer-shell electronsmetallic character
Adecreasesdecreases
Bdecreasesincreases
Cincreasesincreases
Dincreasesdecreases
  1. 1

    Outer-shell electrons increase from left to right, so the answer is C or D.

  2. 2

    Metallic character decreases: D. [1]

3. Group number and ion charge

The group number is linked to the charge on the ions. Group I elements form 1+ ions, Group II elements form 2+ ions and Group III elements form 3+ ions.

Elements in Group VII have 7 outer-shell electrons and form ions with a 1– charge.

Examiner insight

“The link between group number and the ion of the elements or the formation of ionic bonds from Group I elements was not well recalled.” “Some candidates did not use the Periodic Table. The charge on the ion is 3+ so it would be from Group III.”

Worked example 11 mark

Answer the following questions using only the elements from the list: aluminium, boron, bromine, carbon, chlorine, helium, hydrogen, magnesium, nitrogen, oxygen, potassium, silver, sodium, zinc. Each element may be used once, more than once or not at all.

Give the name of the element that forms an ion with a 3+ charge.

  1. 1

    A 3+ ion comes from Group III: aluminium (boron is also accepted). [1]

4. Same group, similar properties

Elements in the same group have similar chemical properties. Their atoms have the same number of outer-shell electrons.

The group number is the number of electrons in the outer shell, not the number of shells. Sodium, with configuration 2,8,1, has one outer-shell electron, so it is in Group I.

Examiner insight

“Many candidates appeared to confuse the number of electrons in the outer shell with the number of electron shells and chose Distractor C.” “Some answers which were closer suggested it was because it required two electrons to have a full outer shell rather than describing the number of electrons it has in the outer shell.”

Worked example 11 mark

Answer the following questions using only the elements from the list: aluminium, boron, bromine, carbon, chlorine, helium, hydrogen, magnesium, nitrogen, oxygen, potassium, silver, sodium, zinc. Each element may be used once, more than once or not at all.

Give the name of the element that has atoms with an electronic configuration of 2,8,1.

  1. 1

    Add the electrons: 2 + 8 + 1 = 11, so the atom has 11 protons.

  2. 2

    One outer-shell electron means Group I; proton number 11 is sodium. [1]

5. Predicting from position

An element's position gives its group, so its number of outer-shell electrons, and the charge on its ion. Its place along the period tells you whether it is a metal or a non-metal.

Use the Periodic Table provided in the exam to check the position of an element you know well.

Examiner insight

“Many candidates did not know why phosphorus is in Group V of the Periodic Table.”

Worked example 13 marks

Element X is in Group II. Predict the number of outer-shell electrons in an atom of X, the charge on its ion, and whether X is a metal or a non-metal.

  1. 1

    Group II: 2 outer-shell electrons. [1]

  2. 2

    Group II elements form ions with a 2+ charge. [1]

  3. 3

    X is on the left of the table, so it is a metal. [1]

7. Group I: the alkali metals

Group I contains the alkali metals. Three of them are lithium, sodium and potassium.

They are relatively soft metals. Compared with transition elements they have low densities and low melting points.

Hardness, strength and high density were not accepted as properties of a Group I metal.

Examiner insight

“These were not accepted because the candidates are expected to know that Group I metals are soft and have low densities.” “Candidates should realise that Group I metals have relatively low density and low melting point and are relatively soft.”

Worked example 12 marks

Group I metals and transition elements are both metals. State two physical properties in which a Group I metal differs from a transition element.

  1. 1

    Group I metals have a lower density. [1]

  2. 2

    Group I metals have a lower melting point. [1]

  3. 3

    Softer, or less hard, is also a correct difference and can replace either one.

8. Melting point decreases down the group

Going down the group, the melting point decreases. Lithium has the highest melting point of the three and potassium the lowest.

So sodium melts at a higher temperature than potassium, and at a lower temperature than lithium.

Examiner insight

“The commonest error was to suggest that the melting point of lithium is below that of sodium.”

Worked example 11 mark

Which statement about alkali metals is correct?

A Lithium is denser than sodium.

B Sodium is more reactive than potassium.

C Sodium has a higher melting point than potassium.

D Potassium has more outer-shell electrons than sodium.

  1. 1

    Sodium is above potassium, so its melting point is higher.

  2. 2

    C: sodium has a higher melting point than potassium. [1]

9. Density increases down the group

Going down the group, the density increases. This is a general trend. Lithium, at the top, has the lowest density.

Melting point and density go in opposite directions. Keep the two trends apart.

Examiner insight

“Although the stronger candidates tended to choose the correct answer more than any other option, weaker candidates tended to choose Distractor C showing recall of the trend in reactivity of Group I elements but not their physical properties.”

Worked example 11 mark

Elements P, Q and R are three elements in Group I of the Periodic Table. Element P has a lower density than element Q. Element Q has a higher melting point than element R. What are elements P, Q and R?

A lithium, sodium, potassium

B sodium, potassium, lithium

C lithium, potassium, sodium

D potassium, lithium, sodium

  1. 1

    Density increases down the group, so P is above Q.

  2. 2

    Melting point decreases down the group, so Q is above R.

  3. 3

    A: P is lithium, Q is sodium, R is potassium. [1]

10. Reactivity increases down the group

Going down the group, the reactivity increases. Lithium is the least reactive of the three and potassium the most.

Potassium is not the most reactive Group I metal. Elements below it, such as rubidium and caesium, are more reactive.

Examiner insight

“Potassium was sometimes chosen as the most reactive, presumably because it is the most reactive candidates have seen.”

Worked example 11 mark

Caesium is a Group I element. Which statement describes a property of caesium?

A It does not conduct electricity.

B It has a higher melting point than sodium.

C It reacts more vigorously with water than potassium.

D It is less dense than lithium.

  1. 1

    Caesium is below potassium, so it is more reactive.

  2. 2

    B and D are wrong: melting point decreases and density increases down the group.

  3. 3

    C: it reacts more vigorously with water than potassium. [1]

12. Predicting a value for another element

To predict a property of another Group I element, place it in the group and follow the trend.

If the melting point decreases, an element below the last one has a lower value. If the density increases, it has a higher value.

An element between two others has a value between theirs. Lithium melts at 180 °C and potassium at 64 °C, so any value from 75 °C to 170 °C was accepted for sodium.

Examiner insight

“In option D, candidates recalled that the density of Group I elements increases down the group but confused the trend in melting point.” “Most candidates completed the table correctly; the commonest errors being to give too high a value for either the melting point of rubidium or the density of lithium.”

Worked example 11 mark

Rubidium, pmbRb, is a Group I metal. It has a density of 1.53 g / cm³ and a melting point of 39 °C. Caesium, pmbCs, is also a Group I metal. Which statement gives the melting point and density of caesium?

A 1.20 g / cm³ and 29 °C

B 1.20 g / cm³ and 49 °C

C 1.90 g / cm³ and 29 °C

D 1.90 g / cm³ and 49 °C

  1. 1

    Caesium is below rubidium: density is higher than 1.53 g / cm³.

  2. 2

    Caesium is below rubidium: melting point is lower than 39 °C.

  3. 3

    C: 1.90 g / cm³ and 29 °C. [1]

13. Predicting a physical state

A metal is a solid below its melting point. It is a liquid between its melting point and its boiling point.

To predict the state, compare the temperature with the melting point. Say that the temperature is below the melting point.

Examiner insight

“The best answers gave the state as ‘solid’ and the reason as ‘50 °C is below the melting point’.” “Many candidates just referred to the value of the melting point without reference to 20 °C being below the melting point while others gave reasons which referred to the boiling point instead of the melting point.”

Worked example 12 marks

Table 2.1 shows some properties of the Group I elements. Deduce the physical state of lithium at 95 °C. Give a reason for your answer.

metalmelting point / °Cboiling point / °Catomic radius / pm
lithium1801342152
sodium–883186
potassium64762–
rubidium39688248
  1. 1

    physical state: solid [1]

  2. 2

    reason: 95 °C is lower than the melting point (180 °C) [1]

Recap

  • Lithium, sodium and potassium are Group I alkali metals. They are relatively soft.
  • Down the group the melting point decreases.
  • Down the group the density increases, as a general trend.
  • Down the group the reactivity increases.
  • Name the direction of a trend. A bare property is not a trend.
  • To predict a value, follow the trend from the neighbouring elements.
  • A metal is solid below its melting point. Compare the temperature with the melting point in the reason.

14. Halogens: diatomic non-metals

The halogens are the elements in Group VII. Chlorine, bromine and iodine are non-metals.

Halogens are diatomic. A molecule has two atoms. The two atoms are in the same molecule, and they are not two types of atom. Write the molecule, not the atom: F₂, Cl₂, Br₂ and I₂.

Examiner insight

“Many candidates did not give a precise enough definition of diatomic, often just referring to “two atoms” instead of implying that they were in the same molecule.” “Common errors included representation of the formula of fluorine as F rather than F2.”

Worked example 11 mark

Halogens exist as diatomic molecules.

Explain what is meant by the term diatomic.

  1. 1

    a molecule that has two atoms (combined) [1]

16. Appearance at r.t.p.

Chlorine is a pale yellow-green gas. Bromine is a red-brown liquid. Iodine is a grey-black solid.

So the physical state changes from gas to liquid to solid down the group. Not every halogen is a gas.

Examiner insight

“Candidates assumed that all of the halogens were gases at room temperature.” “Some candidates gave the colour of another halogen.”

Worked example 12 marks

State the colour and the physical state of bromine at r.t.p.

  1. 1

    colour: red-brown [1]

  2. 2

    physical state: liquid [1]

17. Displacement reactions

A more reactive halogen displaces a less reactive halogen from a solution of its halide. This type of reaction is displacement.

Name the halogen and the halide carefully. Chlorine is a halogen. Potassium chloride is a halide. Chlorine displaces bromine from potassium bromide, and bromine displaces iodine from potassium iodide.

Cl₂ + 2NaI → I₂ + 2NaCl

Br₂ + 2NaI → I₂ + 2NaBr

Examiner insight

“Other common errors included the suggestion of interhalogen compounds such bromine iodide or to repeat the products iodine and potassium bromide as the reactants.” “This year candidates forgot the difference between a halogen and a halide and wrote down ‘chloride’ and ‘potassium bromine’.”

Worked example 13 marks

Aqueous chlorine reacts with aqueous sodium iodide to produce aqueous iodine and aqueous sodium chloride.

(i) State the name of this type of reaction.

(ii) Complete the symbol equation for this reaction. Cl₂ + ...NaI → ... + 2NaCl

  1. 1

    (i) displacement [1]

  2. 2

    (ii) Cl₂ + 2NaI → I₂ + 2NaCl: the number 2 before NaI [1]

  3. 3

    the product I₂ [1]

18. Explaining displacement

To explain a displacement, compare two halogens by name. The order of reactivity is chlorine, then bromine, then iodine.

Chlorine displaces bromine and iodine. Bromine displaces iodine only. If the halogen added is less reactive than the one in the halide, there is no reaction.

Examiner insight

“In (d)(iii), candidates who simply stated ‘bromine is more reactive’ gained no credit as it was not clear what bromine was more reactive than?” “The commonest errors were to compare the reactivity of iodine with chloride, to state that ‘iodine is less reactive than potassium’ or ‘iodine is less reactive than potassium chloride’.”

Worked example 11 mark

Explain why aqueous iodine does not react with aqueous sodium bromide.

  1. 1

    iodine is less reactive than bromine [1]

19. Predicting properties

Use the trends to predict an element you are not told about. Fluorine is above chlorine: a gas, less dense than chlorine, and more reactive than chlorine.

Astatine is below iodine: a solid, denser than iodine, and less reactive than iodine. Its molecule is At₂. For a value, choose one between the values of its neighbours.

Examiner insight

“Candidates needed to use their knowledge of the trends in Group VII to predict that astatine was a solid.” “The best answers stated that fluorine is more reactive than chlorine.”

Worked example 15 marks

Use the information in Table 2.1 to answer the following questions.

(i) Predict the melting point of iodine.

(ii) Predict the density of iodine at room temperature and pressure.

(iii) Deduce the physical state of bromine at –1 °C. Give a reason for your answer.

(iv) Predict the physical state of fluorine at room temperature and pressure.

halogenmelting point in °Cboiling point in °Cdensity at room temperature and pressure in g / cm³
chlorine–101–350.0032
bromine–7+593.1
iodine+184
astatine+302+3378.93
  1. 1

    (i) a value between –6 °C and +183 °C [1]

  2. 2

    (ii) a value between 3.2 and 8.9 g / cm³ [1]

  3. 3

    (iii) liquid [1]

  4. 4

    –1 °C is higher than the melting point (–7 °C) and lower than the boiling point (+59 °C) [1]

  5. 5

    (iv) gas [1]

Recap

  • Group VII halogens are diatomic non-metals: F₂, Cl₂, Br₂, I₂.
  • Down the group, density increases and reactivity decreases.
  • Chlorine is a pale yellow-green gas, bromine a red-brown liquid, iodine a grey-black solid.
  • A more reactive halogen displaces a less reactive halogen from its halide: a displacement reaction.
  • Always compare two named halogens: ‘bromine is more reactive than iodine’.
  • Keep halogen and halide apart: chlorine, but potassium chloride.
  • To predict, follow the trends: fluorine is a more reactive gas, astatine a less reactive solid.

20. High density and high melting point

The transition elements are metals with high densities and high melting points.

Group I metals are different. They have relatively low density and low melting point.

Asked how transition elements differ from Group I metals, give melting point and density.

Examiner insight

“A few candidates were confused with the properties and used low melting point and low density.” “Candidates should realise that Group I metals have relatively low density and low melting point and are relatively soft.”

Worked example 12 marks

Titanium is a transition element that can be used as a catalyst. State two other properties of transition elements.

  1. 1

    high densities [1]

  2. 2

    high melting point (or high boiling point) [1]

21. Transition elements as catalysts

Transition elements often act as catalysts, as elements and in compounds.

In the Haber process the catalyst is iron, Fe. With alkenes and hydrogen the catalyst is nickel, Ni.

From a list of metals, pick the transition element as the likely catalyst and give that as the reason.

Examiner insight

“Platinum was probably the most often suggested metal as a catalyst from the list of five, but few candidates gave the reason that platinum was the only transition element in the list. Many candidates thought it was because platinum was (relatively) inert.”

Worked example 12 marks

The symbols of elements with atomic numbers 21 to 30 are given in Table 1.1. Give the symbol of the element that:

(a) is the catalyst in the Haber process

(d) is the catalyst used in the reaction of alkenes with hydrogen

atomic number21222324252627282930
symbol of elementScTiVCrMnFeCoNiCuZn
  1. 1

    (a) Fe [1]

  2. 2

    (d) Ni [1]

22. Coloured compounds

Transition elements form coloured compounds. The colour belongs to the compound, not to the metal.

Ammonium dichromate, (NH₄)₂Cr₂O₇, is an orange solid. The chromium in it is the element that causes the colour.

Examiner insight

“The commonest error was to suggest the elements themselves are coloured rather than the compounds.” “Others suggested that chromium itself was a coloured metal.”

Worked example 11 mark

Ammonium dichromate, (NH₄)₂Cr₂O₇, is an orange solid. Identify the element which causes ammonium dichromate to be coloured.

  1. 1

    chromium / Cr [1]

23. Variable oxidation numbers

The ions of a transition element can have variable oxidation numbers. The same element forms more than one ion.

The Roman numeral in a name is the oxidation number of the element. In copper(II) oxide the oxidation number of copper is +2. Always write the sign: a bare 2 is not an oxidation number.

A redox reaction needs a change in oxidation number. Chromate(VI) and dichromate(VI) both contain chromium(VI), so converting one into the other shows no change in oxidation number.

copper(I) oxide: Cu₂O

nickel(II) nitrate: Ni(NO₃)₂

chromium(III) oxide: Cr₂O₃

Examiner insight

“Candidates struggled to give the key detail that the Roman numeral (II) in the name copper(II) oxide means that the oxidation number of copper is +2.” “Candidates need to be aware that a key part of an oxidation number is the positive or negative sign preceding the integer. Integers alone are not oxidation numbers.”

Worked example 12 marks

Write the formulas of the following compounds of transition elements.

copper(I) oxide

nickel(II) nitrate

  1. 1

    copper(I) oxide: Cu₂O [1]

  2. 2

    nickel(II) nitrate: Ni(NO₃)₂ [1]

24. Iron(II) and iron(III)

Iron forms two ions, iron(II), Fe²⁺, and iron(III), Fe³⁺.

When iron(II) changes to iron(III), the oxidation number of iron rises from +2 to +3. The iron(II) is oxidised to iron(III). Name both ions: a vague reference to 'iron' is not enough.

Examiner insight

“Only better performing candidates realised that iron(II) had been oxidised to iron(III) in Experiment 3.” “Vague references to iron were common and several candidates thought chromium ions were present.”

Worked example 13 marks

A solution contains iron(II) ions, Fe²⁺. The solution is left in air and the ions change into iron(III) ions, Fe³⁺.

(a) State the oxidation number of iron in each ion.

(b) Name the type of change that happens to the iron(II) ions.

  1. 1

    (a) in Fe²⁺: +2 [1]

  2. 2

    in Fe³⁺: +3 [1]

  3. 3

    (b) oxidation: iron(II) is oxidised to iron(III) [1]

Recap

  • Transition elements are metals with high densities and high melting points.
  • Group I metals have relatively low density and low melting point.
  • Transition elements form coloured compounds. The element itself is not described as coloured.
  • They often act as catalysts: Fe in the Haber process, Ni for alkenes with hydrogen.
  • Extended: transition element ions have variable oxidation numbers, for example iron(II) and iron(III).
  • Extended: the Roman numeral in a name is the oxidation number. Write it with its sign, as in +2.

25. Group VIII: unreactive gases

The noble gases form Group VIII of the Periodic Table. Helium He, neon Ne, argon Ar and krypton Kr are examples.

They are gases at room temperature and pressure. They are unreactive: they do not react with water, and they do not react with oxygen to give an acidic oxide.

Examiner insight

“A considerable number of candidates thought that argon is reactive or just stated that argon is a noble gas.”

Worked example 11 mark

Which statements about elements in Group VIII of the Periodic Table are correct?

1 Atoms of the elements have full outer electron shells. 2 They are diatomic. 3 They are gaseous at room temperature and pressure. 4 They react with water.

A 1 and 3 · B 1 and 4 · C 2 and 3 · D 2 and 4

  1. 1

    A: 1 and 3. They have full outer shells and are gaseous. They are not diatomic and do not react with water. [1]

26. Monatomic, not diatomic

A noble gas is monatomic. Its particles are single atoms, not molecules.

Oxygen and nitrogen exist as diatomic molecules. A noble gas does not.

Write neon as Ne, never Ne₂.

Examiner insight

“Noble gases are monatomic. Candidates did not realise this.”

Worked example 11 mark

Which statements about noble gases are correct?

1 Their atoms have complete outer shells of electrons. 2 They exist as diatomic molecules. 3 They are in Group VIII of the Periodic Table. 4 They react with oxygen to give an acidic oxide.

A 1 and 3 · B 1 and 4 · C 2 and 3 · D 2 and 4

  1. 1

    A: 1 and 3. Noble gases are monatomic, so 2 is wrong. They are unreactive, so 4 is wrong. [1]

27. Why they are unreactive

The reason lies in electronic configuration. An atom of a noble gas has a full outer shell of electrons. Neon is 2,8 and argon is 2,8,8: each has a complete outer shell.

Examiner insight

“The best answers suggested that ‘the outer shell is full’ or ‘there is a complete outer shell of electrons’.”

Worked example 12 marks

An atom of neon has the electronic configuration 2,8. Explain why neon is unreactive.

  1. 1

    The outer shell of neon holds 8 electrons. This is a full outer shell. [1]

  2. 2

    A full outer shell of electrons makes neon unreactive. [1]

28. Helium is the exception to eight

Helium has only two electrons. It has one shell, and that shell is full with two. Neon and argon have eight electrons in the outer shell, so ‘eight outer electrons’ is not true of every noble gas. Write ‘full outer shell’.

Examiner insight

“Many candidates mistakenly assumed that helium has eight outer shell electrons rather than just two.”

Worked example 12 marks

Helium is unreactive. Explain why, in terms of its electronic configuration.

  1. 1

    Helium has the electronic configuration 2. [1]

  2. 2

    Its outer shell is full, so helium is unreactive. [1]

Recap

  • Group VIII: the noble gases are unreactive, monatomic gases.
  • They are unreactive because the atoms have a full outer shell of electrons.
  • Neon is 2,8, argon is 2,8,8. Helium is 2 and is full.

End-of-chapter exercise

Test yourself on the whole chapter. Work through these before moving on.

  1. State what the order of the elements in the Periodic Table is based on.1 mark
  2. Name (a) the horizontal rows and (b) the vertical columns of the Periodic Table.2 marks
  3. Describe how metallic character changes from the left to the right of a period.2 marks
  4. State the charge on the ion formed by an element in (a) Group II and (b) Group VII.2 marks
  5. Sodium and potassium are both in Group I. Explain why their chemical properties are similar.2 marks
  6. An element has atoms with the electronic configuration 2,8,2. State its group number, the charge on its ion and whether it is a metal or a non-metal.3 marks
  7. Phosphorus is in Group V. Explain why, and predict whether it is a metal or a non-metal.3 marks
  8. Sodium is more reactive than lithium. Potassium is more reactive than sodium. State the trend in reactivity down Group I and predict whether rubidium is more or less reactive than potassium.2 marks
  9. The table gives information about four Group VII elements, in order going down the group. (a) Describe the trend in boiling point down Group VII. (b) A student predicts that the boiling point of chlorine is −120 °C. Explain why this value fits the trend in boiling point but cannot be correct. Give the range in which the boiling point of chlorine must lie. | element | melting point / °C | boiling point / °C | | --- | --- | --- | | fluorine | −220 | −188 | | chlorine | −101 | not given | | bromine | −7 | 59 | | iodine | 114 | 184 |4 marks
  10. The table gives information about four Group II elements, in order going down the group. (a) Describe the trend in atomic radius down Group II and predict the atomic radius of barium. (b) A student says that melting point decreases down Group II. Explain why the student is not correct. (c) Predict the charge on a barium ion. Explain why barium is chemically similar to magnesium. | element | atomic radius / nm | melting point / °C | | --- | --- | --- | | magnesium | 0.160 | 650 | | calcium | 0.197 | 842 | | strontium | 0.215 | 777 | | barium | not given | 727 |6 marks
  11. Group I elements are known by a common name. State the name.1 mark
  12. A student describes sodium as a hard metal with a high density and a high melting point. Correct the three mistakes.3 marks
  13. Lithium melts at 180 °C. Potassium is lower in Group I. Does potassium melt above or below 180 °C?1 mark
  14. Rubidium is below potassium in Group I. Compare the reactivity of rubidium with that of potassium.1 mark
  15. Rubidium has a density of 1.53 g / cm³. Is potassium more dense or less dense than rubidium?1 mark
  16. Put lithium, sodium and potassium in order of increasing melting point. Then put them in order of increasing reactivity.2 marks
  17. Lithium melts at 180 °C and boils at 1342 °C. Deduce the physical state of lithium at 250 °C. Give a reason for your answer.2 marks
  18. Lithium, sodium and potassium melt at 180 °C, 98 °C and 64 °C. Which of 39 °C, 75 °C or 120 °C is the most likely melting point of rubidium? Explain.2 marks
  19. The table below gives data for four Group I metals. A sample of one of these metals, M, is a solid at 50 °C and a liquid at 80 °C. (a) Identify M. Explain your answer. (b) Deduce the physical state, at 50 °C, of the metal directly below M in the group. Give a reason. (c) Caesium is below rubidium. A student predicts that caesium melts at 49 °C. Explain why this prediction does not fit the trend. | metal | melting point / °C | boiling point / °C | | --- | --- | --- | | lithium | 180 | 1342 | | sodium | 98 | 883 | | potassium | 64 | 762 | | rubidium | 39 | 688 |5 marks
  20. W, X, Y and Z are lithium, sodium, potassium and rubidium, but not in that order. Rubidium is below potassium in Group I. W is more reactive than Y. Y has a lower melting point than Z. X has a higher density than W. (a) Identify W, X, Y and Z. Explain how you used each piece of information. (b) Z melts at 180 °C and W melts at 64 °C. A student predicts that Y melts at 50 °C. Explain why this prediction must be wrong. (c) The student also says that X is the most reactive element in Group I. Explain why this is wrong.7 marks
  21. State what is meant by the term diatomic. Write the formula of a molecule of chlorine.2 marks
  22. State the colour and the physical state of chlorine, bromine and iodine at r.t.p.3 marks
  23. Put chlorine, bromine and iodine in order of reactivity, most reactive first. State which of the three has the greatest density.2 marks
  24. Chlorine is added to aqueous potassium bromide. Name the two products.2 marks
  25. Aqueous bromine is added to aqueous potassium iodide. Name the type of reaction and write the balanced symbol equation.3 marks
  26. Aqueous iodine is added to aqueous sodium chloride. State and explain what happens.2 marks
  27. Aqueous bromine is added to separate samples of aqueous sodium chloride and aqueous sodium iodide. State which sample reacts. Name the products. Explain both results.4 marks
  28. Astatine is the halogen below iodine in Group VII. (a) Predict the physical state of astatine at r.t.p. and give the formula of a molecule of astatine. (b) Predict whether aqueous astatine displaces iodine from aqueous potassium iodide. Explain your answer.4 marks
  29. The table gives data for four halogens. Room temperature is 25 °C. (a) Predict the boiling point of fluorine. Give two reasons for your choice. (b) Deduce the physical state of iodine at 150 °C. Give a reason for your answer. (c) At r.t.p. the density of chlorine is 0.0032 g / cm³ and the density of bromine is 3.1 g / cm³. Use the table to explain why the density of bromine is so much greater. | halogen | melting point in °C | boiling point in °C | | --- | --- | --- | | fluorine | –220 | | | chlorine | –101 | –35 | | bromine | –7 | +59 | | iodine | +114 | +184 |6 marks
  30. Halogens X, Y and Z are chlorine, bromine and iodine, not in that order. Each halogen is added to the aqueous potassium halide of another. The table gives the results. (a) Deduce which halogen is X, Y and Z. Explain your answer. (b) Write the balanced symbol equation for the reaction of X with the potassium halide of Z. (c) State the colour and physical state of Y at r.t.p. (d) Astatine is below iodine in Group VII. Predict whether Y reacts with aqueous sodium astatide, NaAt. Explain your answer and write the balanced symbol equation for any reaction. | mixture | result | | --- | --- | | X added to the potassium halide of Y | reaction | | X added to the potassium halide of Z | reaction | | Y added to the potassium halide of Z | no reaction |8 marks
  31. State whether transition elements have high or low densities.1 mark
  32. Metal Z has a low density, a low melting point and forms white compounds. Explain why Z is not a transition element.2 marks
  33. A student writes: 'Chromium is an orange metal.' Correct the statement.1 mark
  34. Nickel is a transition element. A student says it is a transition element because it is shiny and conducts electricity. Give two properties that identify nickel as a transition element.2 marks
  35. Name the transition element used as the catalyst in: (a) the Haber process (b) the reaction of alkenes with hydrogen.2 marks
  36. Data for three elements, P, Q and R, are given in the table. Identify the transition element. Give three reasons from the table. | element | density | melting point | compounds | | --- | --- | --- | --- | | P | high | high | green and blue | | Q | low | low | white | | R | low | high | white |4 marks
  37. The oxide ion is O²⁻. Write the formula of copper(I) oxide.1 mark
  38. Chromium forms chromate(VI) ions, CrO₄²⁻, and dichromate(VI) ions, Cr₂O₇²⁻. (a) State the oxidation number of chromium in each ion. (b) Explain why changing chromate(VI) ions into dichromate(VI) ions is not a redox reaction.2 marks
  39. Vanadium is a metal. The table gives the colours of four solutions that contain vanadium. (a) Give two pieces of evidence from the table that vanadium is a transition element. (b) Another solution is added to the violet solution. It turns green, then blue. State the oxidation number of vanadium in the violet solution and in the blue solution. (c) Name the type of change to the vanadium in (b). Explain in terms of oxidation number. | vanadium in the solution | vanadium(II) | vanadium(III) | vanadium(IV) | vanadium(V) | | --- | --- | --- | --- | --- | | colour of the solution | violet | green | blue | yellow |6 marks
  40. Iron is a transition element. It forms two chlorides, A and B. The chloride ion is Cl⁻. In A there are two chloride ions for each iron ion, and in B there are three. A solution of A is pale green. Chlorine gas is bubbled through it and it turns yellow as B forms in solution. (a) Deduce the name of A. Explain how you worked it out. (b) Write the formula of B. (c) Write the symbol equation, with state symbols, for the solution of A reacting with chlorine. (d) State the change in oxidation number of iron and name the type of change to the iron.7 marks
  41. Name the Group of the Periodic Table that contains the noble gases.1 mark
  42. State two properties of the noble gases.2 marks
  43. Give the meaning of the word monatomic.1 mark
  44. Write the formula of krypton gas.1 mark
  45. State the number of electrons in the outer shell of helium.1 mark
  46. An atom of argon has the electronic configuration 2,8,8. Explain why argon is unreactive.2 marks
  47. A student says: ‘Neon is unreactive because its electronic structure is not complete.’ Correct the student.2 marks
  48. A sealed lamp contains a hot metal filament in a gas X. Each atom of X has 10 electrons. (a) Deduce the electronic configuration of an atom of X. (b) Explain why X does not react with the hot filament.3 marks
  49. The table gives the electronic configurations of atoms of four elements, Q, R, S and T. (a) Identify the two noble gases. (b) A student says: ‘Only S is a noble gas, because a noble gas has eight outer electrons.’ Explain the student’s mistake. (c) Another student says: ‘T has two outer electrons, like helium, so T is unreactive.’ Explain why this is wrong. | element | electronic configuration | | --- | --- | | Q | 2 | | R | 2,6 | | S | 2,8,8 | | T | 2,8,8,2 |4 marks
  50. Hot magnesium reacts with the oxygen in air. A welder joins two pieces of hot magnesium inside a stream of argon gas. An atom of argon has the electronic configuration 2,8,8. (a) Explain why argon is used. Refer to electronic configuration in your answer. (b) A student says: ‘Helium could not replace argon, because a helium atom has only two electrons in its outer shell.’ Explain why the student is wrong.5 marks

Go deeper

Practise and revise with member-only material for this chapter.

Workbook

Exam-style practice questions with full worked solutions.

Unlock with a plan

Chapter at a Glance

A single-page summary of every key idea for fast revision.

Unlock with a plan

Free notes are just the start.

Unlock every Workbook and Chapter at a Glance, and generate your own worksheets and predicted papers.

Explore plans

Related chapters

Solids, liquids and gasesElements, compounds and mixturesFormulaeElectrolysisExothermic and endothermic reactionsPhysical and chemical changes