Edexcel A-Level Chemistry AS 2 Atomic Structure and the Periodic Table Questions

Practise atomic structure, isotope notation, mass spectra and ionisation energy data using tables, spectra and particle counts.

Exam points

interpret isotope notation to find protons, neutrons and electrons in atoms or ions
draw or read mass spectra, including molecular ion peaks for diatomic molecules
use successive ionisation energy tables to deduce an element and explain jumps

Covered syllabus points

2.1—The structure of an atom in terms of electrons, protons and neutrons 2.2—The relative mass and charge of protons, neutrons and electrons 2.3—What is meant by the terms ‘atomic (proton) number’ and ‘mass number’2.4—The atomic number and the mass number to determine the number of each type of subatomic particle in an atom or ion 2.5—The term ‘isotope’2.6—The basic principles of a mass spectrometer 2.7—Predict mass spectra 2.8—Define first, second and third ionisation energies and understand that all ionisation energies are endothermic 2.9—An orbital is a region within an atom that can hold up to two electrons with opposite spins 2.10—How ionisation energies are influenced by the number of protons in the nucleus, the electron shielding and the sub-shell 2.11—Ideas about electronic structure developed from: i an understanding that successive ionisation energies provide evidence 2.12—The shapes of s and p orbitals 2.13—Orbitals in sub-shells: i each take a single electron before pairing up ii pair up with two electrons of opposite spin 2.14—Predict the electronic configuration of atoms of the elements from hydrogen to krypton inclusive and their ions 2.15—Electronic configuration determines the chemical properties of an element 2.16—The Periodic Table is divided into blocks, such as s, p and d, and know the number of electrons that can occupy s, p and d 2.17—Represent data, in a graphical form (including the use of logarithms of first ionisation energies on a graph) for elements 1 2.18—Explain: i the trends in melting and boiling temperatures of the elements of Periods 2 and 3 of the Periodic Table in terms

[Maximum number: 1]

Which statement about subatomic particles is correct?

neutral atoms always contain the same number of protons and electrons

neutral atoms always contain the same number of protons and neutrons

electrons have a relative mass of 1 and a charge of -1

protons have a relative mass of 1 and no charge

[Maximum number: 2]

The table shows some data about fundamental particles in an atom.

Table for Question 2 — Edexcel A-Level Chemistry AS

(a)

An atom of hydrogen can be represented as ${ }^{1} \mathrm{H}$ .

What is the mass, in grams, of this hydrogen atom?

$1.6725 \times 10^{-24}$

$1.6734 \times 10^{-24}$

$3.3473 \times 10^{-24}$

$3.3482 \times 10^{-24}$

[ 1 ]

(b)

Which of the particles would be deflected by an electric field?

electrons only

electrons and protons only

neutrons and protons only

electrons, neutrons and protons

[ 1 ]

[Maximum number: 3]

Atomic numbers and mass numbers are used to identify isotopes.

(a)

What is the mass number of the isotope ${ }_{36}^{84} \mathrm{Kr}$ ?

120

[ 1 ]

(b)

Which element has the atomic number 15 and mass number 31?

[ 1 ]

(c)

What is the number of electrons in the selenide ion ${ }_{34}^{80} \mathrm{Se}^{2-}$ ?

[ 1 ]

[Maximum number: 1]

The table shows some data about fundamental particles in an atom.

Table for Question 4 — Edexcel A-Level Chemistry AS

Which of the particles would be deflected by an electric field?

electrons only

electrons and protons only

neutrons and protons only

electrons, neutrons and protons

[Maximum number: 2]

This question is about copper and its compounds.

A sample of copper contains the isotopes ${ }^{63} \mathrm{Cu}$ and ${ }^{65} \mathrm{Cu}$ .

Complete the table to show the numbers of subatomic particles in the atoms of these two isotopes of copper.

Table for Question 5 — Edexcel A-Level Chemistry AS

One mark for each correct row
Four or five correct scores one mark
Ignore working

Isotope

Protons

Neutrons

Electrons

${ }^{63} \mathrm{Cu}$

29

34

29

(1)

${ }^{65} \mathrm{Cu}$

29

36

29

[Maximum number: 1]

This question is about magnesium, magnesium oxide and magnesium sulfate.

A sample of magnesium contains three isotopes and has a relative atomic mass of 24.32.
The table gives the relative abundances of two of these isotopes.

Table for Question 6 — Edexcel A-Level Chemistry AS

State one similarity and one difference between these isotopes.

[Maximum number: 5]

This question is about magnesium, magnesium oxide and magnesium sulfate.

(a)

A sample of magnesium contains three isotopes and has a relative atomic mass of 24.32.
The table gives the relative abundances of two of these isotopes.

Table for Question (a) — Edexcel A-Level Chemistry AS

[ 5 ]

(i)

Calculate the relative abundance and hence the mass number of the third isotope.
Give your answer to the appropriate number of significant figures.
You must show all your working.

[ 4 ]

An answer that makes reference to the following points:

- calculation of the % abundance of the third isotope

(1)

- substitute equation

(1)

- calculation of the mass of the $3^{\text {rd }}$ isotope

(1)

- answer to 2 SF only

(1)

Example of calculation

100-78.99-10.00=11.01(%)

$24.32=\frac{(24 \times 78.99)+(25 \times 10)+(y \times 11.01)}{100}$ $\mathrm{y}=\frac{2432-(24 \times 78.99)-(25 \times 10)}{11.01}$

y=25.998

(ii)

State which of these isotopes would be deflected most in a mass spectrometer. Justify your answer.

[ 1 ]

An answer that makes reference to the following point:

- ${ }^{24} \mathrm{Mg}$ and lowest mass or lowest m / z ratio (so deflected more by the magnetic field)

Allow ${ }^{24} \mathrm{Mg}$ is lightest Allow ${ }^{24} \mathrm{Mg}^{+}$

Ignore just the lowest mass

(1)

[Maximum number: 2]

Naturally occurring bromine has two isotopes: bromine-79 and bromine-81.

The mass spectrum of a sample of bromine is obtained.

On the mass spectrum grid, draw the peaks for the bromine molecular ions, showing the relative peak heights.

The bromine isotopes in this sample have the same relative abundance.

Relative abundance

[Maximum number: 2]

Ionisation energies provide information about the orbitals in the electronic structures of atoms.

Write the equation for the second ionisation energy of fluorine.

Include state symbols.

equation

- state symbols

(1)

(1)

Example of equation
$\mathrm{F}^{+}(\mathrm{g}) \rightarrow \mathrm{F}^{2+}(\mathrm{g})+\mathrm{e}^{(-)}$

Allow

$\mathrm{F}^{+}(\mathrm{g})-\mathrm{e}^{(-)} \rightarrow \mathrm{F}^{2+}(\mathrm{g})$

Ignore state symbols on the electron

Allow TE for M2 is if the $1^{\text {st }}$ or $3^{\text {rd }}$ ionisation equation is shown.

[Maximum number: 2]

This question is about the structure of atoms.

State what is meant by the term orbital.

[Maximum number: 1]

This question is about the structure of atoms.

Suggest why the fourth ionisation energies of neon and sodium are similar in magnitude even though the elements are in different periods of the Periodic Table.

[Maximum number: 3]

This question is about the structure of atoms.

Describe what can be deduced about the electronic structure of sodium from its successive ionisation energies.

[Maximum number: 1]

This question is about the structure of atoms.

State the shape of an s orbital and the shape of a p orbital.

[Maximum number: 1]

The graph shows the first ionisation energies of some consecutive elements from Periods 2 and 3 of the Periodic Table.

The letters used to label the elements are not their chemical symbols.

Figure for Question 14 — Edexcel A-Level Chemistry AS

Which element has only one p orbital containing a pair of electrons?

element U

element V

element W

element X

[Maximum number: 1]

This question is about the element calcium and some of its compounds.

Give the complete electronic configuration, using s, p, d notation, of a calcium atom in the ground state.

An answer that makes reference to the following point:

- $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2}$

Accept correct electrons-in-boxes notation

Accept expansion of p -subshell(s), eg $2 \mathrm{p}_{\mathrm{x}}{ }^{2} 2 \mathrm{p}_{\mathrm{y}}{ }^{2} 2 \mathrm{p}_{\mathrm{z}}{ }^{2}$ for $2 \mathrm{p}^{6}$

Allow non-superscript numbers for electrons

Ignore use of commas and spaces

Ignore 2,8,8,2

Ignore [Ar] for $1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2} 2 \mathrm{p}^{6} 3 \mathrm{~s}^{2} 3 \mathrm{p}^{6}$

Do not award incorrect order of subshells

[Maximum number: 1]

This question is about copper and its compounds.

A sample of copper contains the isotopes ${ }^{63} \mathrm{Cu}$ and ${ }^{65} \mathrm{Cu}$ .

State why the two isotopes of copper have the same chemical reactions.

[Maximum number: 1]

Each response gives the atomic numbers of two elements. Which pair of atomic numbers are those of elements that are in different blocks of the Periodic Table?

5,9

10,16

13, 18

16, 20

[Maximum number: 4]

This question is about the structure of atoms.

(a)

The log of the fourth ionisation energy for six elements is shown in the table.

Plot a graph of these data.
(3)

Figure for Question (a) — Edexcel A-Level Chemistry AS

[ 3 ]

(b)

Use your graph to estimate the fourth ionisation energy for sodium, in $\mathrm{kJ} \mathrm{mol}^{-1}$ .

[ 1 ]

[Maximum number: 3]

This question is about the bonding in the elements of Period 3 in the Periodic Table. The melting temperatures of the Period 3 elements are shown in the table.

Table for Question 19 — Edexcel A-Level Chemistry AS

Explain why the melting temperature of silicon is much higher than that of phosphorus, by referring to their structures.

An explanation that makes reference to the following points:

- phosphorus (P) simple molecular

- silicon (Si) giant (covalent/molecular) structure

- when phosphorus melts weak London forces are broken and when silicon melts strong covalent bonds are broken

(1)

Allow (small) molecules/ $\mathrm{P}_{4} /$ just 'molecular'/simple
covalent

All question bank results loaded

Covered syllabus points

Question 1

Question 2

Question (a)

Question (b)

Question 3

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Question (b)

Question (c)

Question 4

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Question 6

Question 7

Question (a)

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Question (ii)

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Question 12

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Question 17

Question 18

Question (a)

Question (b)

Question 19