Atomic Structure (AQA A Level Chemistry)

Exam Questions

3 hours45 questions
1a3 marks

The plum pudding model of an atom was derived by JJ Thompson in the nineteenth century.  He suggested that the atom was a sphere of positive charge which contained negative electrons like plums in a pudding. This type of model of element A is shown in Figure 1.

A circle with scattered short horizontal lines inside, unevenly spaced across the interior, on a plain white background.

Give three differences of the plum pudding model compared to the modern day model of an atom.

1b2 marks

Identify element A in Figure 1 and give a reason for your answer.

1c1 mark

Give the electron configuration of element A.

1d2 marks

Write an equation including state symbols to show the first ionisation energy of element A.

1e2 marks

Explain why the first ionisation energy of element A is less that the second ionisation energy of element A.

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2a2 marks

Naturally occurring isotopes of Europium are shown in Table 1.

Table 1

m/z value

151

153

Abundance 

47.8 %

52.2 %

Calculate the relative atomic mass of Europium. Give your answer to 1 d.p. 

2b2 marks

In terms of particles, explain why Europium-151 and Europium-153 have similar chemical properties.

2c2 marks

Define the term relative atomic mass.

2d2 marks

The main isotopes of Gadolinium and Dysprosium have relative atomic masses that are larger than Europium.

Table 2

Isotope

Atomic Number

Gadolinium-158

    64

Dysprosium-164

    66

Use the information Table 2 to calculate the number of neutrons in Gadolinium and Dysprosium. 

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3a4 marks

The relative abundance of isotopes of an element can be measured using a mass spectrometer.

Antinomy, Sb, is used in lead alloys to make them harder. A sample of antinomy was analysed in the mass spectrometer and two main isotopes were found, 121Sb and 123Sb. 

State the number of protons and neutrons in both 121Sb and 123Sb of antimony.

3b2 marks

Explain how the gaseous sample of antimony, Sb, can be ionised in the mass spectrometer.

3c2 marks

Name the relevant part of the mass spectrometer and explain how the abundance of the antimony isotope is measured. 

3d2 marks

Explain which ion of antimony, 121Sb+ or 123Sb+, will be deflected more in a mass spectrometer.

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4a1 mark

Figure 1 shows the first ionisation energies of elements in Period 3. 

Graph showing 1st ionisation energy (kJ/mol) on the y-axis for elements Na, Mg, Al, Si, P, S, Cl, Ar, increasing from left to right.

Figure 1

Plot an ‘X’ on the diagram to show the first ionisation energy of silicon, Si.

4b1 mark

Explain why the first ionisation energy of magnesium, Mg, is higher than the first ionisation energy of aluminium, Al.

4c1 mark

Write an equation to show the second ionisation energy of aluminium, Al.

4d1 mark

Give the full electronic configuration of a sulfide, S2-, ion. 

4e4 marks

Explain the trend in ionisation energies down Group 2.

4f1 mark

The first ionisation energy for sodium, Na, is 495.8 kJ mol-1.

Explain why the energy change for this reaction is endothermic.

4g2 marks

Table 1 contains information about the relative abundance of different isotopes of magnesium.

Table 1

m/z value

24

25

26

Relative abundance (%)

78.99

10.00

11.01

Calculate the relative atomic mass of magnesium. Give your answer to 2 decimal places. 

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5a1 mark

An isotope of an element X has two more protons than and two more neutrons than an atom of K41.

Use the periodic table to identify element X.

5b3 marks

Give the full electronic configuration of the following species:

  • K+

  • Ti

  • Co

5c2 marks

Ionisation energy reactions are endothermic processes.

Write the equations for the first ionisation energy of K and the second ionisation energy of Sc.

5d1 mark

Give the full electronic configuration of the Sc2+ ion.

5e2 marks

Table 1 shows successive ionisation energies of element Z in Period 3. 

Table 1

Ionisation energy

1

2

3

4

5

(kJ mol-1)

786

1576

3232

4356

16091

Explain why the first ionisation energy generally increases from left to right across the periodic table. 

5f3 marks

Using the data in Table 1, state and explain which group of the periodic table element Z belongs to.

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1a2 marks

Atoms are made up of three subatomic particles; protons, neutrons and electrons. 

Table 1 below shows data about these particles.

Table 1

Particle

Proton

Neutron

Electron

Mass / kg

1.673 × 10-27

1.675 × 10-27

9.000 × 10-31

Use the data from Table 1, and the Periodic Table, to calculate the mass of one atom of carbon in kg. 

1b1 mark

12C, 13C and 14C are all isotopes of carbon.

State the difference between these three isotopes in terms of subatomic particles. 

1c2 marks

A student claims that the different isotopes of carbon will have different chemical properties. 

State and explain whether the the student is correct. 

1d4 marks

Table 2 shown below contains data on the relative isotopic abundance of a chemical element, E. 

Table 2

Relative m/z

46

47

48

49

50

% abundance

8.02

7.31

73.81

X

5.32

Complete Table 2 by calculating ‘X’.

1e1 mark

Use the data from Table 2 to calculate the relative atomic mass, Ar, to 1 decimal place and use the Periodic Table to identify the element, E. 

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2a3 marks

A and B are different chemical elements, from different groups in the Periodic Table.

Explain why mA and nA have identical chemical properties, but mA and pB have different chemical properties. 

2b3 marks

An atom has twice as many protons, and twice as many neutrons, as an atom of 19F. 

Determine the chemical symbol of this atom, including the mass number and the number of electrons.

2c1 mark

Elements exist as a mixture of isotopes.

Name an instrument which would be used to measure the relative abundances of isotopes of an element. 

2d2 marks

Describe the graph which would be produced by the piece of equipment identified in part (c).

2e3 marks

Explain how that graph and the data obtained could be used to calculate the relative atomic mass of an element. 

2f1 mark

Helium has been found to react with sodium and form a stable compound.

This discovery by scientists was very unexpected. Explain why.

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3a2 marks

This question is about atomic structure. 

Write the full electron configuration for Ca and Ca2+.

3b2 marks

All elements have a value for a first ionisation energy. 

Define the term first ionisation energy of an element.

3c1 mark

Write the equation for the first ionisation energy of calcium.

3d2 marks

Table 1 below gives the successive ionisation energies of a Period 3 element. 

Table 1

Ionisation number

1st

2nd

3rd

4th

5th

6th

7th

8th

Ionisation energy (kJ mol-1)

738

1450

7734

10543

13630

18020

21711

25661

Identify the element, justifying your choice.

3e3 marks

Explain why the value of the first ionisation energy of calcium is higher than that of potassium.

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4a2 marks

TOF (time of flight) mass spectrometry is a powerful instrumental method of analysis. 

Describe how ions are formed in a TOF (time of flight) mass spectrometer.

4b3 marks

In a TOF (time of flight) mass spectrometer, the ions formed are accelerated, detected and their abundance is determined.

Explain how these three steps occur. 

4c2 marks

An element, Z, has 4 isotopes, 82Z, 83Z, 84Z and 86Z.

Write an equation, including state symbols, to show how an atom of element Z is ionised by electron impact. Give the m/z value of the ion that would reach the detector first.

4d4 marks

In a TOF mass spectrometer, the time of flight, t, of an ion is shown by the equation

t space equals space d square root of fraction numerator m over denominator 2 K E end fraction end root

Where d is the length of the flight tube in metres, m is the mass of an ion in kg and KE is the kinetic energy of the ions in the mass spectrometer. 

The time of flight of a 82Z+ ion is 1.243 × 10−5 s

KE of an ion in the flight tube is 1.029 × 10−15 J

The Avogadro constant, L, is 6.022 x 1023 mol-1 

Calculate the time of flight of the 84Z+ ion.

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5a3 marks

The Bohr model of an atom represents a central nucleus, consisting of protons and neutrons, with electrons surrounding it moving in circular orbits. This model was proposed by Niels Bohr in 1913 and after some further research, energy levels and sublevels were recognised, and the model was refined.  

Using your knowledge of atomic structure, complete Table 1 below for the particles found in an atom. 

Table 1

Particle

Relative charge

Relative mass

Proton

 

 

Neutron

 

 

Electron

 

 

5b2 marks

State the block in the Periodic Table in which silicon is placed and explain your answer.

5c1 mark

A mass spectrometer can be used to detect isotopes of an element, such as silicon. For these to be detected in the mass spectrometer, a sample containing the isotopes must first be vapourised and then ionised.

State why the sample must be ionised.

5d1 mark

The graph below in Figure 1 shows the mass spectrum of a sample of silicon.

Bar chart displaying relative abundance against m/z ratio. Peaks at m/z 28 and 29 are prominent; smaller peak at m/z 30.

Using Figure 1, calculate the relative atomic mass, Ar, of this sample of silicon to 1 decimal place. 

5e1 mark

Suggest why the relative atomic mass on the Periodic Table might be different to the relative atomic mass of a sample analysed using a mass spectrometer. 

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1a2 marks

Successive ionisation energies provide the evidence for the arrangement of electrons in atoms.

Write the equation, including state symbols for the third ionisation energy of oxygen.

1b2 marks

Table 1 shows the successive ionisation energies of oxygen.

Table 1

Ionisation number

1

2

3

4

5

6

7

8

Ionisation energy (kJ mol-1)

1314

3388

5301

7469

10989

13327

71337

84080

Explain how this data shows evidence of two energy shells in oxygen.

1c3 marks

Give the full electron configuration of the following atoms and ions.

  • Tellurium, Te

  • Zinc(II) ion, Zn2+ 

  • Copper(I) ion, Cu+ 

1d3 marks

Chlorine has two naturally occurring isotopes. 35Cl with a mass of 34.969 and 37Cl with a mass of 36.966. The relative atomic mass of Cl is 35.5.

Calculate the abundance of each isotope to 2 d.p.

1e1 mark

In order to ionise the sample of chlorine atoms in the Time of Flight (TOF) mass spectrometer, the sample must be ionised. 

Suggest why electron bombardment would be a more suitable method for a sample of chlorine, rather than electrospray ionisation. 

1f2 marks

Predict whether the atomic radius of 35Cl or 37Cl would be the greatest and give a reason for your answer. 

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2a4 marks

A sample of Cerium, Ce, was analysed in a Time of Flight (TOF) mass spectrometer. The relative abundances of three of the four main isotopes that were identified are shown in Table 1

A sample of Cerium, Ce, has four isotopes that have a known relative abundance. This sample has an Ar of 140.12.

Table 1

Isotope

136Ce

138Ce

140Ce

mCe

Abundance (%)

0.19

0.25

88.45

To be calculated 

Use the data from Table 1 to calculate m, the mass number and the abundance of isotope mCe. 

2b1 mark

A time of flight (TOF) mass spectrum for a sample of Cerium, Ce, was obtained. The sample analysed was ionised by electron impact.

Identify the ion of Cerium, Ce, in Table 1 with the shortest time of flight and justify your answer.

2c5 marks

An 86Sr+ ion travels through the TOF mass spectrometer with a kinetic energy of 1.921 x 10-15 J. 

The ion takes 1.09 x 10-5 s to reach the detector. 

Calculate the length of the flight tube in meters. Give your answer to 3 significant figures.

    KE = 1 halfmv2     v = d over t    L = 6.02 x 1023

2d4 marks

A 79Se+ ion travels through the flight tube with an energy of 6.27 x 10-16 J.

Calculate the velocity of the ion.

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3a3 marks

A sample of element Z was extracted from a meteorite. Table 1 shows the relative abundance of each isotope in a mass spectrum of this sample of Z.

Table 1

m/z value

64

66

67

68

Relative abundance (%)

38.9

27.8

14.7

18.6

Calculate, to 1 d.p., the relative atomic mass of Z and suggest an identity of Z.

3b5 marks

TOF (time of flight) mass spectrometry is a powerful instrumental method of analysis. In order to obtain a mass spectrum of Z, a gaseous sample must first be ionised.

Describe how ionisation takes place and give two reasons why ionisation is necessary. Include an equation to show the process of ionisation.

3c2 marks

Sometimes in the mass spectrum on Z a very small peak with an m/z value of 32 is present.

Explain the occurrence of this peak.

3d2 marks

Calculate the mass of a single 68Z+ ion in kg. Assume the mass of the 68Z+ is the same as the 68Z atom. Give your answer to 3 significant figures.

(The Avogadro Constant L = 6.02 x 1023)

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4a1 mark

Amorphous, unorganised solid form, boron is used as a rocket fuel igniter and in pyrotechnic flares.

Write an equation, including state symbols to show the process that occurs when the first ionisation of boron, B, is measured. 

4b1 mark

Suggest why the ionisation energy of boron is lower than that of beryllium going against the general trend in ionisation energies across the period.

4c2 marks

Give the definition of relative isotopic mass.

4d3 marks

A naturally occurring sample of the element boron, B, has two isotopes and a relative atomic mass of 10.8.

Calculate the relative abundances of both isotopes in the sample of boron, B.

4e1 mark

Ions of boron, B, are deflected in a TOF mass spectrometer. Give one reason why isotopes of the same mass and velocity are deflected by different amounts in the same magnetic field.

4f2 marks

A sample of another group three element Aluminum, Al, is analysed in a TOF mass spectrometer. The 27Al+ ion travelled down a 5 m flight tube with a kinetic energy of 1.45 x 10-13 J.

KE = begin mathsize 16px style 1 half end stylemv2     v = d over t     L = 6.02 x 1023

Calculate the mass of 1 aluminium atom in kg.

4g2 marks

Use the information in part (f) to calculate the velocity of the Al+ ion travelling through the flight tube.

4h1 mark

Use the information in parts (f) and (g) to calculate its time of flight. 

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5a1 mark

Give the full electron configuration of the Cu+ ion. 

5b2 marks

A sample of copper atoms were placed through a TOF mass spectrometer. Two isotopes of copper were detected, one of them being 63Cu and the other being 65Cu.

v space equals space d over t

Calculate the velocity of the 63Cu if it travels down a 5 m flight tube in 4.200 x 10-6 s. Give your answer to 3 significant figures.

5c3 marks

Calculate the percentage relative abundance of 63Cu with a mass of 62.9296 and 65Cu with a mass of 64.9278, when the average mass of the Cu isotope is 63.546. Give your answer to 3 significant figures.

5d1 mark

Zirconium is another transition metal that is primarily used in a catalytic converter in cars. 

Give the electron configuration for the zirconium 2+ ion, Zr2+, starting with [Kr]. 

5e1 mark

Write the equation including state symbols to represent the third ionisation energy of zirconium, Zr.

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