Revision Library

revisionlibrary.co.uk

GCSE · Chemistry

C1b The Periodic Table: Groups and Trends

AQA 8464 · Calculator allowed · about 85 minutes

Total Marks

Name: _______________________________ Date: ____ / ____ / ______

Answer ALL questions. Show all your working.

How the Periodic Table Was Built

Original text written for Revision Library.

By the 1860s, over 60 elements had been discovered, and chemists were looking for a way to organise them. In 1864, John Newlands arranged the known elements in order of atomic weight and noticed that every eighth element seemed to share similar properties, an idea he called the Law of Octaves. His table was not widely accepted, partly because it broke down after the first twenty or so elements and grouped some very different elements together. In 1869, Dmitri Mendeleev produced a more successful table. He also ordered elements by atomic weight, but where the pattern did not quite fit, he swapped the order of a few elements so that those with similar properties lined up in the same column. Crucially, he left gaps for elements he believed had not yet been discovered, and used the pattern of the table to predict their properties. When elements such as gallium and germanium were later discovered with properties very close to those predicted, Mendeleev's table gained wide acceptance. The modern periodic table keeps this basic layout but orders elements by atomic (proton) number rather than atomic weight, which resolves a small number of anomalies. Elements in the same vertical column, or group, have the same number of electrons in their outer shell, which gives them similar chemical properties.

This question is about the layout of the modern periodic table. Complete each sentence.

(a)The horizontal rows of the periodic table are called ______.(1)

(b)The vertical columns of the periodic table are called ______.(1)

(c)Elements in the same group have the same number of ______.(1)

(d)Approximately what proportion of all the elements in the periodic table are metals?(1)

(Total for Question 1 is 4 marks)

John Newlands arranged the known elements in order of atomic weight in 1864.

(a)Describe the pattern Newlands identified in his 'Law of Octaves'.(1)

(b)Give two reasons why other scientists did not accept Newlands' table.(2)

(Total for Question 2 is 3 marks)

Dmitri Mendeleev published his periodic table in 1869.

(a)State one way Mendeleev's table was different from Newlands' table.(1)

(b)Explain how Mendeleev used the gaps in his table, and why this later led to his table being widely accepted.(2)

(c)State why the noble gases (Group 0) do not appear anywhere in Mendeleev's original 1869 table.(1)

(Total for Question 3 is 4 marks)

Tellurium (Te) has a relative atomic mass of 127.6 and an atomic number of 52. Iodine (I) has a relative atomic mass of 126.9 and an atomic number of 53.

(a)Explain why iodine is placed after tellurium in the modern periodic table, even though iodine has a lower relative atomic mass.(2)

(b)State one advantage of arranging the periodic table by atomic number rather than atomic mass.(1)

(Total for Question 4 is 3 marks)

State whether each property below is typical of metals or of non-metals.

(a)Shiny (lustrous), malleable, and a good conductor of heat and electricity.(1)

(b)Dull in appearance, brittle when solid, and a poor conductor of electricity.(1)

(c)Low density, and often a gas at room temperature.(1)

(d)Forms a positive ion when it reacts.(1)

(Total for Question 5 is 4 marks)

This question is about the chemical differences between metals and non-metals.

(a)State the general type of ion formed when a metal atom reacts.(1)

(b)State the general type of ion formed when a non-metal atom reacts.(1)

(c)State whether metal oxides are generally acidic or basic.(1)

(Total for Question 6 is 3 marks)

Table 1 shows the melting points of the first three Group 1 (alkali) metals.

Metal	Melting point (degC)
Lithium	180.5
Sodium	97.8
Potassium	63.5

(a)Describe the trend in melting point shown by Table 1 as you go down Group 1.(1)

(b)Give two other physical properties that are unusual for metals but are true of the Group 1 metals.(2)

(Total for Question 7 is 3 marks)

Potassium reacts vigorously when a small piece is added to water.

(a)Balance the symbol equation for this reaction: ___K(s) + ___H2O(l) -> ___KOH(aq) + ___H2(g)(2)

(b)State three observations you would expect to make when potassium reacts with water.(3)

(Total for Question 8 is 5 marks)

Aaliyah carries out flame tests as part of the required practical 'Identification of ions by chemical and flame tests', to help identify the metal in four unlabelled compounds, W, X, Y and Z.

(a)Describe how Aaliyah should carry out a flame test on one of the samples.(3)

(b)Explain why the wire loop is first dipped in dilute hydrochloric acid and held in the flame until it produces no colour, before each new sample is tested.(2)

(c)Table 2 shows known flame colours: lithium = crimson/red, sodium = yellow/orange, potassium = lilac. Aaliyah observes that sample W gives a lilac flame and sample X gives a yellow/orange flame. Identify the metal present in sample W and in sample X.(2)

(Total for Question 9 is 7 marks)

The alkali metals (Group 1) become more reactive as you go down the group.

(a)State how the reactivity of Group 1 metals changes down the group.(1)

(b)Explain this trend in terms of atomic size and the distance of the outer electron from the nucleus.(2)

(Total for Question 10 is 3 marks)

Use these relative atomic masses (Ar): H = 1, Li = 7, O = 16, K = 39.

(a)Calculate the relative formula mass (Mr) of lithium hydroxide, LiOH.(1)

(b)Calculate the relative formula mass (Mr) of potassium hydroxide, KOH.(1)

(c)Calculate the difference between the two Mr values found in (a) and (b).(1)

(Total for Question 11 is 3 marks)

Table 1 (question 7) shows melting points of 180.5 degC for lithium, 97.8 degC for sodium, and 63.5 degC for potassium.

Figure (to be drawn): Blank grid provided: x-axis = position in Group 1 (Li, Na, K, Rb), evenly spaced; y-axis = melting point (degC), scale 0 to 200 with gridlines every 20 degC.

(a)Plot the three data points on the grid provided and describe the trend shown.(1)

(b)Use the pattern in the data to estimate the melting point of rubidium (Rb), the next metal down Group 1. Show your method.(2)

(c)Suggest one reason why the value found in (b) is only an estimate.(1)

(Total for Question 12 is 4 marks)

Chlorine, bromine and iodine are the first three halogens (Group 7) commonly studied at GCSE.

(a)State the type of molecule formed by halogen elements such as chlorine (Cl2).(1)

(b)State the state of matter (solid, liquid or gas) of chlorine, bromine and iodine at room temperature.(3)

(Total for Question 13 is 4 marks)

The halogens (Group 7) become less reactive as you go down the group.

(a)State how the reactivity of the halogens changes down Group 7.(1)

(b)Explain this trend in terms of atomic size and the distance of the outer shell from the nucleus.(2)

(Total for Question 14 is 3 marks)

Halogens react with metals to form metal halide salts.

(a)Balance the symbol equation for the reaction of sodium with chlorine: ___Na(s) + Cl2(g) -> ___NaCl(s)(1)

(b)Write a fully balanced symbol equation, including state symbols, for the reaction of iron with chlorine to form iron(III) chloride, FeCl3.(3)

(Total for Question 15 is 4 marks)

Chlorine water is added to separate test tubes of potassium bromide solution and potassium iodide solution.

(a)Predict what would be observed in each test tube.(2)

(b)Write a fully balanced symbol equation, including state symbols, for the reaction between chlorine and potassium bromide solution.(3)

(c)Predict whether a reaction would occur if iodine solution were added to potassium chloride solution. Give a reason for your answer.(1)

(Total for Question 16 is 6 marks)

Freya carries out the required practical investigating the rate of a reaction, using the reaction between small pieces of Group 1 metals and water. She measures the volume of hydrogen gas produced over time using a gas syringe, in order to compare the reactivity of lithium and potassium.
Table 3

Time (s)	0	10	20	30	40
Volume of gas from lithium (cm3)	0	6	11	15	18
Volume of gas from potassium (cm3)	0	18	30	38	42

(a)Identify one hazard in this practical and state a control measure Freya should use to reduce the risk.(2)

(b)State two variables that should be kept the same for this to be a fair test.(2)

(c)Using Table 3, calculate the mean rate of gas production for potassium between 0 and 20 seconds.(2)

(d)Using Table 3, explain how the results support the trend that reactivity increases down Group 1.(1)

(Total for Question 17 is 7 marks)

Table 4 shows the boiling points of four halogens.

Halogen	Boiling point (degC)
Fluorine	-188
Chlorine	-34
Bromine	59
Iodine	184

Figure (to be drawn): Blank grid provided: x-axis = halogen (F, Cl, Br, I, At), evenly spaced; y-axis = boiling point (degC), scale -200 to 400 with gridlines every 50 degC.

(a)Describe the trend in boiling point shown by Table 4 down Group 7.(1)

(b)Explain this trend in terms of the size of the halogen molecules and the intermolecular forces between them.(2)

(c)Use the pattern in Table 4 to estimate the boiling point of astatine (At), the next halogen down Group 7. Show your method.(2)

(Total for Question 18 is 5 marks)

The noble gases (Group 0) are found in the final column of the periodic table.

(a)State the type of particle noble gas elements exist as.(1)

(b)Describe the trend in boiling point down Group 0.(1)

(c)State why the noble gases are described as inert.(1)

(d)Give one everyday use of helium and one everyday use of argon, linking each use to a property of the gas.(2)

(Total for Question 19 is 5 marks)

Table 5 shows the results when solutions of three unknown halogens, X, Y and Z, are each added to potassium chloride, potassium bromide and potassium iodide solutions (R = reaction/colour change seen, NR = no reaction).

Halogen added	+ KCl(aq)	+ KBr(aq)	+ KI(aq)
X	NR	R	R
Y	NR	NR	R
Z	NR	NR	NR

(a)Use the results in Table 5 to place X, Y and Z in order of reactivity, most reactive first.(1)

(b)Explain your answer to (a), using the results in Table 5.(2)

(c)Suggest which real halogen X could be, giving a reason for your answer.(1)

(Total for Question 20 is 4 marks)

Use your knowledge of electron shells and atomic size to answer this question.

Compare and explain the trends in reactivity down Group 1 (the alkali metals) and down Group 7 (the halogens).

(Total for Question 21 is 6 marks)

Mark scheme · C1b The Periodic Table: Groups and Trends

Question 1

(a) B1 periods
(a) Answer: Periods
(b) B1 groups
(b) Answer: Groups
(c) B1 electrons in their outer shell (outer electrons) oe
(c) Answer: Electrons in their outer shell
(d) B1 the majority / more than three-quarters (accept any reasonable estimate over half) oe
(d) Answer: The majority of elements (more than about three-quarters) are metals

Question 2

(a) B1 every eighth element had similar properties to the first (oe)
(a) Answer: Every eighth element in his table had similar properties
(b) B1 the pattern only worked for the first few rows / broke down after calcium (oe)
(b) B1 some groups contained elements with very different properties, e.g. iron placed in the same group as carbon and oxygen (oe)
(b) B1 no gaps were left for elements that had not yet been discovered (oe) - any two of these three reasons for full marks
(b) Answer: Any two of: the pattern broke down after the first twenty or so elements; some groups mixed together elements with very different properties (e.g. metals and non-metals); no gaps were left for undiscovered elements

Question 3

(a) B1 he sometimes swapped the order of elements to keep those with similar properties in the same group, even though this went against strict atomic weight order (oe); OR he left gaps in the table
(a) Answer: He left gaps in the table and sometimes changed the strict order of atomic weight to keep similar elements together
(b) M1 he left gaps where he predicted an undiscovered element should fit, based on the pattern of properties in the table
(b) A1 when elements such as gallium and germanium were later discovered with properties very close to his predictions, this confirmed the table was correct and it became widely accepted (oe)
(b) Answer: Mendeleev left gaps and predicted the properties of the missing elements; when elements matching these predictions (e.g. gallium, germanium) were discovered, scientists accepted his table
(c) B1 the noble gases had not yet been discovered in 1869 (oe)
(c) Answer: The noble gases had not yet been discovered

Question 4

(a) M1 the modern periodic table is arranged in order of increasing atomic (proton) number, not atomic mass (oe)
(a) A1 iodine has a higher atomic number than tellurium (53 compared with 52), so it is placed after tellurium despite having a slightly lower atomic mass (oe)
(a) Answer: The table is ordered by atomic number, and iodine (53) has a higher atomic number than tellurium (52), so it comes after tellurium despite its slightly lower atomic mass
(b) B1 elements with similar properties are grouped together correctly / avoids anomalies where the mass order would separate similar elements (oe)
(b) Answer: Elements with similar chemical properties are correctly grouped together, avoiding the anomalies that atomic mass order would cause

Question 5

(a) B1 metal
(a) Answer: Metal
(b) B1 non-metal
(b) Answer: Non-metal
(c) B1 non-metal
(c) Answer: Non-metal
(d) B1 metal
(d) Answer: Metal

Question 6

(a) B1 a positive ion (cation) oe
(a) Answer: A positive ion (cation)
(b) B1 a negative ion (anion) oe
(b) Answer: A negative ion (anion)
(c) B1 basic (non-metal oxides are generally acidic) cao
(c) Answer: Basic

Question 7

(a) B1 melting point decreases down the group (oe)
(a) Answer: Melting point decreases down Group 1
(b) B1 low density - lithium, sodium and potassium are less dense than water and float on it (oe)
(b) B1 soft enough to be cut with a knife / shiny when freshly cut but tarnish quickly in air (any one) oe
(b) Answer: Any two of: low density (float on water), soft (can be cut with a knife), shiny when freshly cut but quickly tarnish

Question 8

(a) M1 2K(s) + 2H2O(l) -> 2KOH(aq) + ... (correct coefficients for K and H2O)
(a) A1 ... -> 2KOH(aq) + H2(g), fully balanced cao
(a) Answer: 2K(s) + 2H2O(l) -> 2KOH(aq) + H2(g)
(b) B1 fizzing/effervescence as hydrogen gas is given off (oe)
(b) B1 the potassium moves rapidly across the surface of the water (oe)
(b) B1 the potassium ignites, giving a lilac flame, and/or a pop or crackling sound is heard (any one) oe
(b) Answer: Any three of: fizzing/bubbles of gas; the potassium moves/skates across the surface; a lilac flame and/or popping sound as it ignites; the solution formed turns universal indicator purple (alkaline)

Question 9

(a) M1 dip a clean nichrome (or platinum) wire loop into the sample (as a solid, paste or solution) (oe)
(a) M1 hold the wire in the clear/blue part of a roaring (fully open air-hole) Bunsen flame (oe)
(a) A1 observe and record the colour of the flame produced
(a) Answer: Dip a clean wire loop in the sample, hold it in the roaring blue flame of a Bunsen burner, and observe the colour produced
(b) M1 this cleans the wire and removes any residue left over from the previous sample (oe)
(b) A1 so that the colour seen for the new sample is not contaminated by a previous result, keeping the identification valid/reliable (oe)
(b) Answer: It cleans off any residue from the last sample, so the flame colour observed is only due to the new sample and the result is valid
(c) B1 W contains potassium (lilac flame)
(c) B1 X contains sodium (yellow/orange flame)
(c) Answer: W = potassium, X = sodium

Question 10

(a) B1 reactivity increases down the group
(a) Answer: Reactivity increases down Group 1
(b) M1 atoms get larger down the group (more electron shells), so the single outer electron is further from the nucleus and more shielded (oe)
(b) A1 this means there is a weaker force of attraction between the nucleus and the outer electron, so it is lost more easily, making the metal more reactive (oe)
(b) Answer: Atoms get larger down the group, so the outer electron is further from the nucleus and more shielded; the weaker attraction means it is lost more easily, so reactivity increases

Question 11

(a) B1 24 cao
(a) Answer: 24
(b) B1 56 cao
(b) Answer: 56
(c) B1 32 cao, ft from (a) and (b)
(c) Answer: 32

Question 12

(a) B1 melting point decreases down the group (oe)
(a) Answer: Melting point decreases down Group 1
(b) M1 valid method shown, e.g. extending the line of best fit on the graph, or noting that the size of each drop in melting point is getting smaller (180.5 to 97.8 is a drop of 82.7 degC; 97.8 to 63.5 is a drop of 34.3 degC) and continuing this pattern
(b) A1 estimate in the range 25 to 50 degC, consistent with the extrapolated trend (allow ecf for a value consistent with the student's own reasonable extrapolation)
(b) Answer: Approximately 35-45 degC (the real melting point of rubidium is 39.3 degC)
(c) B1 it is extrapolated beyond the data given / assumes the pattern continues in exactly the same way, which may not be true (oe)
(c) Answer: It is extrapolated beyond the given data, assuming the same pattern continues, which may not be exactly correct

Question 13

(a) B1 diatomic (a molecule made of two atoms) oe
(a) Answer: Diatomic (two atoms joined together)
(b) B1 chlorine: gas cao
(b) B1 bromine: liquid cao
(b) B1 iodine: solid cao
(b) Answer: Chlorine = gas, bromine = liquid, iodine = solid

Question 14

(a) B1 reactivity decreases down the group
(a) Answer: Reactivity decreases down Group 7
(b) M1 atoms get larger down the group (more electron shells), so the outer shell, where an extra electron would be gained, is further from the nucleus and more shielded (oe)
(b) A1 this means there is a weaker force of attraction for the incoming electron, so it is harder to gain an electron, making the halogen less reactive (oe)
(b) Answer: Atoms get larger down the group, so the outer shell is further from the nucleus and more shielded; the weaker attraction for an incoming electron means it is harder to gain, so reactivity decreases

Question 15

(a) B1 2Na(s) + Cl2(g) -> 2NaCl(s), fully balanced cao
(a) Answer: 2Na(s) + Cl2(g) -> 2NaCl(s)
(b) M1 correct formulae for reactants and product: Fe, Cl2, FeCl3
(b) M1 correctly balanced: 2Fe + 3Cl2 -> 2FeCl3
(b) A1 correct state symbols: 2Fe(s) + 3Cl2(g) -> 2FeCl3(s) cao
(b) Answer: 2Fe(s) + 3Cl2(g) -> 2FeCl3(s)

Question 16

(a) B1 potassium bromide solution: colour change to orange/yellow as bromine is formed (oe)
(a) B1 potassium iodide solution: colour change to brown as iodine is formed (oe)
(a) Answer: Potassium bromide solution turns orange/yellow (bromine forms); potassium iodide solution turns brown (iodine forms)
(b) M1 correct formulae: Cl2, KBr, KCl, Br2
(b) M1 correctly balanced: Cl2 + 2KBr -> 2KCl + Br2
(b) A1 correct state symbols: Cl2(aq) + 2KBr(aq) -> 2KCl(aq) + Br2(aq) cao
(b) Answer: Cl2(aq) + 2KBr(aq) -> 2KCl(aq) + Br2(aq)
(c) B1 no reaction, because iodine is less reactive than chlorine, so it cannot displace chloride ions from solution (oe)
(c) Answer: No reaction; iodine is less reactive than chlorine so cannot displace the chloride ions

Question 17

(a) M1 hazard: hydrogen gas produced is flammable, and/or the potassium may ignite or spit (oe)
(a) A1 control measure: keep naked flames away from the apparatus, and/or use a safety screen and only a small piece of metal (oe)
(a) Answer: Hazard: flammable hydrogen gas (and potassium may ignite/spit). Control: keep flames away, use a safety screen and only a small piece of metal
(b) B1 the volume of water used each time
(b) B1 the size/mass (surface area) of the piece of metal used each time
(b) Answer: Any two of: volume of water, size/mass of the metal piece, temperature of the water
(c) M1 correct substitution: rate = volume / time = 30 / 20
(c) A1 1.5 cm3/s (allow cm3 s^-1) cao
(c) Answer: 1.5 cm3/s
(d) B1 potassium produces gas faster than lithium (a greater volume of gas in the same amount of time / steeper initial rate), showing potassium reacts more quickly/vigorously, which supports potassium being more reactive than lithium (oe)
(d) Answer: Potassium produces gas much faster than lithium (e.g. 30 cm3 vs 11 cm3 at 20 s), showing it reacts more vigorously, supporting the trend that reactivity increases down Group 1

Question 18

(a) B1 boiling point increases down the group
(a) Answer: Boiling point increases down Group 7
(b) M1 the halogen molecules get larger (more electrons) down the group (oe)
(b) A1 so there are stronger intermolecular (van der Waals) forces between molecules, which need more energy to overcome, raising the boiling point (oe)
(b) Answer: Molecules get larger down the group, so intermolecular forces between them are stronger and need more energy to overcome, raising the boiling point
(c) M1 valid extrapolation method shown, e.g. extending the line of best fit, or finding the gaps between values (154, 93, 125 degC) and continuing a similar-sized increase
(c) A1 estimate in the range 220 to 400 degC (allow ecf for a value consistent with a reasonable extrapolation shown)
(c) Answer: Approximately 300-310 degC (the true value is very uncertain, as astatine is extremely rare and radioactive)

Question 19

(a) B1 monatomic (single, separate atoms, not molecules) oe
(a) Answer: Monatomic (single atoms)
(b) B1 boiling point increases down the group
(b) Answer: Boiling point increases down Group 0
(c) B1 they have a full outer shell of electrons, so do not readily react or form bonds (oe)
(c) Answer: They have a full outer shell of electrons, so are very unreactive
(d) B1 helium is used in party/weather balloons because it has a very low density (oe)
(d) B1 argon is used in filament light bulbs or welding because it is unreactive/inert, so it does not react with the hot filament or molten metal (oe)
(d) Answer: Helium in balloons (low density); argon in light bulbs/welding (unreactive, protects hot metal from reacting)

Question 20

(a) B1 X, then Y, then Z (most to least reactive) cao
(a) Answer: X > Y > Z
(b) M1 X displaces halide ions from both potassium bromide and potassium iodide, so X must be more reactive than the halogens already combined in both of these salts; Y only displaces from potassium iodide, so Y is less reactive than X but more reactive than Z (any valid comparison) oe
(b) A1 none of X, Y or Z reacts with potassium chloride, showing that none of them is more reactive than the halogen already in that salt, i.e. all three are the same as or less reactive than that halogen (oe)
(b) Answer: X displaces halide ions from both KBr and KI, showing it is the most reactive; Y only displaces from KI, so is next most reactive; Z displaces neither, so is least reactive. None displaces from KCl, showing none is more reactive than the halogen already present in it
(c) B1 chlorine, because it is the most reactive of the three unknowns and, like X, chlorine is known to displace both bromide and iodide ions from solution (oe, allow ecf for a reasoned alternative consistent with the data)
(c) Answer: X could be chlorine, as chlorine is known to displace both bromide and iodide ions from solution, matching the reactivity pattern shown by X

Question 21

Level 3 (5-6): A clear, detailed and accurate comparison of both trends, correctly explaining each in terms of atomic size and electron shells, with the opposite direction of the two trends clearly identified and explained (metals lose an electron, halogens gain one).
Level 2 (3-4): The trend for at least one group is described and explained in terms of atomic size/electron shells; some comparison between the two groups is attempted but may be incomplete or only partly correct.
Level 1 (1-2): Simple statement(s) of the trend(s) (e.g. Group 1 becomes more reactive, Group 7 becomes less reactive down the group), with little or no linked explanation.
Level 0 (0): No relevant content.
Indicative content:
- Group 1: reactivity increases down the group.
- Group 1 atoms get larger down the group (more electron shells).
- The single outer electron is further from the nucleus and more shielded, so it is held less strongly / the attraction between the nucleus and outer electron is weaker.
- This makes the outer electron easier to lose, so Group 1 metals react more readily going down the group (e.g. potassium reacts more vigorously with water than lithium).
- Group 7: reactivity decreases down the group.
- Group 7 atoms get larger down the group (more electron shells).
- The outer shell, where an extra electron would be gained, is further from the nucleus and more shielded.
- This makes it harder to attract and gain an extra electron, so Group 7 elements react less readily going down the group (e.g. chlorine can displace bromine and iodine from solution, but iodine can displace neither).
- The two trends are in opposite directions because Group 1 elements react by losing an electron, which becomes easier further from the nucleus, whereas Group 7 elements react by gaining an electron, which becomes harder further from the nucleus.

The Periodic Table: Groups and Trends - Worksheets, Questions and Revision