Atomic structure — AS & A Level Chemistry (9701) questions by topic
Ionisation-energy patterns and electron configuration questions dominate this topic: comparing successive ionisation energies to identify an unknown Period 3 element, completing nucleon, neutron and electron counts for an isotope of tellurium, and explaining first-ionisation-energy graph trends.
State, identify, deduce, explain and draw top the command words across 44 questions from 2023 to 2025 papers, worth from 1 to 22 marks, where confusing nucleon number with neutron number is a recurring pitfall. Checking each configuration and graph-shape answer with instant marking flags a missing principal quantum number or an incorrectly dipped ionisation-energy graph before either error is repeated in a later structure question.
What examiners look for
- A recurring criticism is interpreting 'nucleon number' as the number of neutrons rather than protons plus neutrons.
- Examiners note omitting the principal quantum number, such as not specifying '1s', or naming 5p instead of the correct lowest-energy sub-shell.
- A common mistake was drawing a graph with an incorrect dip in ionisation energy, most often placed at the 6th or 7th value.
- Strong answers recognised that a smooth increase from the 5th to 8th ionisation energy indicates silicon, since those electrons all come from the same shell with comparable energies.
- Candidates who correctly distinguished nucleon number, neutron number and electron number for the same isotope scored well.
May–June 2025, Paper 11
The first seven ionisation energies of an element between lithium and neon in the Periodic Table are shown. 1310 3390 5320 7450 11000 13300 71000 kJ mol^-1 What is the outer…
Answer this question and get it marked →Which statement about a 3p orbital is correct? A It can hold a maximum of six electrons. B It has the highest energy of the orbitals with principal quantum number 3. C It is at a…
Answer this question and get it marked →May–June 2025, Paper 12
How many neutrons are contained in an atom of iron with a mass number of 60? A 26 B 30 C 34 D 60
Answer this question and get it marked →May–June 2025, Paper 13
Which isolated gaseous atom has a total of five electrons occupying spherically shaped orbitals? A sodium B fluorine C boron D potassium
Answer this question and get it marked →Why is the second ionisation energy of sodium larger than the second ionisation energy of magnesium? A The attraction between the nucleus and the outer electron is greater in Na^+…
Answer this question and get it marked →May–June 2025, Paper 14
The diagram shows the logarithm of the first 13 ionisation energies of an element. The graph shows a large jump between electrons 2 and 3. Which statement is correct? A A proton…
Answer this question and get it marked →Which graph represents the number of unpaired electrons in the atoms of six elements in Period 3 of the Periodic Table (proton numbers 13–18)? A Monotonically increasing B…
Answer this question and get it marked →May–June 2025, Paper 21
May–June 2025, Paper 22
(i) Define relative atomic mass. (ii) Use Table 2.1 to calculate the relative isotopic mass of the third isotope of iron in the sample. Show your working.
Answer this question and get it marked →May–June 2025, Paper 23
(i) Give the full electronic configuration of a fluorine atom. (ii) Deduce the number of pairs of electrons in the second energy shell, n = 2, of an oxygen atom. (iii) Draw the…
Answer this question and get it marked →May–June 2024, Paper 11
Z is a compound of two elements, X and Y. Element X shows a very large increase between its 5th and 6th ionisation energies. It has the second largest 1st ionisation energy in its…
Answer this question and get it marked →Which statement about (131,53)I is correct? A A negative ion of (131,53)I contains 53 neutrons and 52 electrons. B A negative ion of (131,53)I contains 53 neutrons and 54…
Answer this question and get it marked →The relative atomic mass of antimony is 121.76. Antimony has two isotopes. The mass numbers of the two isotopes differ by two. The isotope with the lower mass number is the more…
Answer this question and get it marked →May–June 2024, Paper 12
The first eight successive ionisation energies for two elements of Period 3 of the Periodic Table are shown in the graphs. The first graph (left element) shows a small rise from…
Answer this question and get it marked →In which pairs are both species free radicals? 1 Cl and O 2 Cl^- and O^2- 3 Cl and O^- 4 Cl^+ and O^2+ A 1, 3 and 4 B 1 and 3 only C 1 only D 2 only
Answer this question and get it marked →May–June 2024, Paper 13
What is the total number of protons, neutrons and electrons present in an ammonium ion with a relative formula mass of 21? number of protons number of neutrons number of electrons…
Answer this question and get it marked →This question is about the first ionisation energies of magnesium and neon. Which row is correct? first ionisation energy type of electron removed from Mg type of electron removed…
Answer this question and get it marked →May–June 2024, Paper 22
Complete Table 1.1 using relevant information from the Periodic Table. Table 1.1 nucleon number proton number number of electrons --- --- --- --- Mg²⁺ 24 Al³⁺ 27
Answer this question and get it marked →October–November 2024, Paper 11
Compound X contains two elements, Y and Z. Element Y is in Period 2 of the Periodic Table. In one atom of element Y, the p sub-shell has all three orbitals occupied; only one of…
Answer this question and get it marked →The diagram shows the mass spectrum of a sample of chlorine. Peaks V, W, X, Y and Z are labelled. Peak V is at m/e ≈ 35 with high intensity (~85); peak W is at m/e ≈ 37 with lower…
Answer this question and get it marked →October–November 2024, Paper 12
Which species contains a different number of electrons from the other three? A ClO₄⁻ B H₂SO₄ C SO₄²⁻ D Te²⁻
Answer this question and get it marked →Which factor causes helium to have a higher first ionisation energy than hydrogen? A In the 1s orbital in helium, electrons are paired. B The lowest energy level in helium is…
Answer this question and get it marked →Vitamin C has the structure shown; it is a five-membered lactone ring (furan-2(5H)-one type) bearing several hydroxyl groups, with molecular formula C₆H₈O₆. The mass spectrum of…
Answer this question and get it marked →October–November 2024, Paper 13
Compound X contains two elements, Y and Z. Element Y is in Period 2 of the Periodic Table. In one atom of element Y, the p sub-shell has all three orbitals occupied; only one of…
Answer this question and get it marked →The diagram shows the mass spectrum of a sample of chlorine. Peaks V, W, X, Y and Z are labelled. Peak V is at m/e ≈ 35 with high intensity (~85); peak W is at m/e ≈ 37 with lower…
Answer this question and get it marked →October–November 2024, Paper 21
Cobalt, rhodium and iridium are metals in the same group of the Periodic Table. The shorthand electronic configuration of cobalt is [Ar]3d⁷4s². Identify what is meant by [Ar] by…
Answer this question and get it marked →October–November 2024, Paper 22
Vanadium, niobium and tantalum are metals in the same group of the Periodic Table. The shorthand electronic configuration of vanadium in the ground state is [Ar]3d³4s². State what…
Answer this question and get it marked →October–November 2024, Paper 23
Cobalt, rhodium and iridium are metals in the same group of the Periodic Table. The shorthand electronic configuration of cobalt is [Ar]3d⁷4s². Identify what is meant by [Ar] by…
Answer this question and get it marked →February–March 2023, Paper 12
Which atom contains four times as many neutrons as the ⁷₃Li atom? A ⁴⁰₂₀Ca B ²⁴₁₂Mg C ³¹₁₅P D ²⁶₁₄Si
Answer this question and get it marked →Which statement about the first ionisation energies of magnesium and neon is correct? A Magnesium has the greater numerical value and both are endothermic. B Magnesium has the…
Answer this question and get it marked →February–March 2023, Paper 42
The most common zinc mineral contains zinc(II) sulfide, ZnS. Complete the electrons in boxes diagram in Fig. 1.1 to show the electronic configuration of a zinc(II) ion. (The…
Answer this question and get it marked →May–June 2023, Paper 11
Element X has six more protons than element Y. Which statement must be correct? A Atoms of element Y are smaller than atoms of element X. B Element X has a full shell of…
Answer this question and get it marked →Four successive ionisation energies (IE) of element E are shown. Element E is in Period 3 of the Periodic Table. fifth IE / kJ mol⁻¹ sixth IE / kJ mol⁻¹ seventh IE / kJ mol⁻¹…
Answer this question and get it marked →May–June 2023, Paper 12
When chlorine gas is analysed in a mass spectrometer, 35Cl+ ions are detected. Which row is correct? number of neutrons in 35Cl+ electronic configuration of 35Cl+ --- --- --- A 17…
Answer this question and get it marked →Which statement is correct? A The first ionisation energy of chlorine is more than the first ionisation energy of argon. B The second ionisation energy of calcium is more than the…
Answer this question and get it marked →May–June 2023, Paper 21
Tellurium is an element in Group 16. The most common isotope of tellurium is 130-Te. Its electronic configuration is [Kr] 4d10 5s2 5p4. Complete Table 1.1 for 130-Te by giving its…
Answer this question and get it marked →October–November 2023, Paper 11
Sodium azide, NaN3, is an explosive used to inflate airbags in cars when they crash. It consists of positive sodium ions and negative azide ions. What are the numbers of electrons…
Answer this question and get it marked →The graph shows the variation of the first ionisation energy with proton number for some elements (the letters P, Q, R, S, T, U, V, W, X are not the actual symbols). Which…
Answer this question and get it marked →October–November 2023, Paper 12
Which particle contains 8 protons, 9 neutrons and 10 electrons? A: oxygen-16 anion, 16O with charge -1. B: 16O with charge 2-. C: 17O with charge -1. D: 17O with charge 2-.
Answer this question and get it marked →The second ionisation energy of oxygen is greater than the second ionisation energy of fluorine. Which factor explains this difference? A: The atomic radius of an oxygen atom is…
Answer this question and get it marked →October–November 2023, Paper 13
Sodium azide, NaN3, is an explosive used to inflate airbags in cars when they crash. It consists of positive sodium ions and negative azide ions. What are the numbers of electrons…
Answer this question and get it marked →The graph shows the variation of the first ionisation energy with proton number for some elements. The letters used are not the actual symbols for the elements. [A graph of first…
Answer this question and get it marked →October–November 2023, Paper 21
The elements phosphorus, sulfur and chlorine are in Period 3 of the Periodic Table. Table 1.1 shows some properties of the elements P to Cl. The first ionisation energy of S is…
Answer this question and get it marked →October–November 2023, Paper 23
The elements phosphorus, sulfur and chlorine are in Period 3 of the Periodic Table. Table 1.1 shows some properties of the elements P to Cl. The first ionisation energy of S is…
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