Topic S3.1 · SL and HL

The periodic table: Classification of elements: notes and practice questions

12 min read Jump to 20 practice questions

Summary

This topic covers the organization of elements in the periodic table and the periodic trends in their properties.
The periodic table classifies elements into periods, groups, and s, p, d, f blocks, identifying metals, metalloids, and non-metals.
The period number corresponds to the outer energy level, and the group number indicates the number of valence electrons.
Key periodic trends include atomic radius, ionic radius, ionization energy, electron affinity, and electronegativity.
Metallic character increases down Group 1, while non-metallic character decreases down Group 17.
Oxidation state represents the number of electrons transferred in bond formation, and can be deduced for atoms in ions or compounds.

How it is examined

Trend explanations are the workhorse, usually 2 to 3 marks, and they want the causal chain: nuclear charge, shielding, atomic radius, then the property. A trend stated without a cause scores one of two. Oxidation state deduction is a 1-mark part and appears in both papers. May 2025 HL Paper 2 TZ1 asked candidates to deduce the oxidation state of S in `[Fe(S₂O₃)₂(H₂O)₂]⁻` for [1], and to explain why a transition element complex is coloured for [3], which needs d-sublevel splitting, absorption of a specific wavelength, and the complementary colour being seen.

Given in the booklet

The periodic table with atomic numbers and relative atomic masses. Ionic and atomic radii, first ionization energies, electron affinities, electronegativities, and melting points. HL: the colour wheel and c = λf. What is recall: group and period names, the direction and reason for every trend, the oxidation state rules.

Key ideas

3.1.1 The periodic table consists of periods, groups and blocks. Students identify the positions of metals, metalloids and non-metals.
3.1.2 The period number shows the outer energy level that is occupied by electrons. Elements in a group have a common number of valence electrons. Students deduce the electron configuration of an atom up to Z = 36 from the element's position, and vice versa.
3.1.3 Periodicity refers to trends in properties of elements across a period and down a group. Students explain the periodicity of atomic radius, ionic radius, ionization energy, electron affinity and electronegativity.
3.1.4 Trends down a group include the increasing metallic character of group 1 elements and the decreasing non-metallic character of group 17 elements. Students describe and explain the reactions of group 1 metals with water, and of group 17 elements with halide ions.

Not assessed

HL: knowledge of different types of magnetism will not be assessed.
HL: students are not expected to know the different d-orbital splitting patterns and their relation to the coordination number.

At HL

3.1.7 Discontinuities occur in the trend of increasing first ionization energy across a period. Students explain how these discontinuities provide evidence for the existence of energy sublevels.
3.1.8 Transition elements have incomplete d-sublevels that give them characteristic properties. Students recognize these properties: variable oxidation state, high melting points, magnetic properties, catalytic properties, formation of coloured compounds, and formation of complex ions with ligands.
3.1.9 The formation of variable oxidation states in transition elements can be explained by the fact that their successive ionization energies are close in value. Students deduce the electron configurations of ions of the first-row transition elements.
3.1.10 Transition element complexes are coloured due to the absorption of light when an electron is promoted between the orbitals in the split d-sublevels. The colour absorbed is complementary to the colour observed. Students apply the colour wheel to deduce the wavelengths and frequencies of light absorbed and observed.

Guiding questions

How does the periodic table help us to predict patterns and trends in the properties of elements?

Linking questions

Nature of science, Structure 1.2 How has the organization of elements in the periodic table facilitated the discovery of new elements?
Structure 2.1, 2.2 How do differences in bonding explain the differences in the properties of metal and non-metal oxides?
Reactivity 3.2 How can oxidation states be used to analyse redox reactions?
Inquiry 2, Tool 2 Why are simulations often used in exploring the trends in chemical reactivity of group 1 and group 17 elements?
Nature of science, Structure 2.3 (HL) What are the arguments for and against including scandium as a transition element?
Reactivity 3.4 (HL) What is the nature of the reaction between transition element ions and ligands in forming complex ions?
Tool 1, Inquiry 2 (HL) How can colorimetry or spectrophotometry be used to calculate the concentration of a solution of coloured ions?

Practice questions

54 questions · 34 easy · 17 medium · 3 hard

Showing 20 of 20

Question 1

EasyPaper 1A · calculator1 mark

Which statement best explains why the atomic radius increases down Group 1 from lithium, Li, to caesium, Cs?

A. The nuclear charge decreases.

B. The number of occupied principal energy levels increases.

C. The attraction between the nucleus and the valence electrons increases.

D. The number of valence electrons increases.

Question 2

MediumPaper 2 · calculator12 marks

(a)

Solid rocket boosters are used to provide large amounts of thrust for spacecraft launches. A common oxidizer used in these boosters is ammonium nitrate, $NH_4NO_3$ .

(a) When ignited, ammonium nitrate decomposes to produce nitrogen gas, oxygen gas, and water vapour. Deduce the balanced chemical equation for this decomposition, including state symbols.

[2]

(b)

(b) Calculate the total number of moles of gas produced from the complete decomposition of 100.0 g of ammonium nitrate.

[3]

(c)

(c) The gaseous products are ejected at a temperature of 800 °C. Calculate the total volume, in $dm^3$ , that these gases would occupy at a pressure of 1.01 × 10⁵ Pa.

[3]

(d)

(d) Explain why water vapour deviates more from ideal gas behaviour than oxygen gas does, especially at lower temperatures and higher pressures.

[2]

(e)

(e) Some advanced propellants use ammonium perchlorate, $NH_4ClO_4$ , which produces toxic chlorine gas, $Cl_2$ , upon decomposition. Suggest, including a relevant equation, one reason why the release of chlorine gas into the atmosphere is an environmental concern.

[2]

Question 3

HardPaper 2 · calculator24 marks

(a)(i)

Antimony (Sb) and Bismuth (Bi) are elements in group 15 of the periodic table.

(a) Antimony has two stable isotopes. 57.21% of antimony atoms contain 70 neutrons and the remainder contain 72 neutrons.

(i) Deduce the nuclear symbol of the isotope of antimony containing 72 neutrons. Use section 6 of the data booklet.

[1]

(a)(ii)

(ii) Calculate, to two decimal places, the relative atomic mass of antimony.

[2]

(b)(i)

Bismuth(III) nitrate, $Bi(NO_3)_3$ , is a common salt of bismuth.

(b) (i) The compound contains both ionic and covalent bonds. State which particles are joined by covalent bonds and which are joined by ionic bonds.

[2]

(b)(ii)

(ii) Distinguish between covalent and ionic bonding in terms of electron distribution.

[2]

(b)(iii)

(iii) State the enthalpy term that characterizes the strength of the bonding between the ions in an ionic solid.

[1]

(b)(iv)

(iv) Write an equation for the formation of aqueous bismuth(III) nitrate from solid bismuth(III) oxide and nitric acid.

[2]

(b)(v)

(v) Calculate the volume, in $cm^3$ , of $1.50 \text{ mol dm}^{-3}$ nitric acid required to react completely with $5.00 \text{ g}$ of solid bismuth(III) oxide.

[3]

(b)(vi)

(vi) Predict, with a reason, whether bismuth(III) oxide is expected to be primarily acidic, basic or amphoteric.

[1]

(b)(vii)

(vii) Discuss how the relative reactivity of zinc and bismuth could be established using the metals and aqueous solutions of their nitrates.

[2]

(b)(viii)

(viii) Discuss the products formed at the electrodes during the electrolysis of aqueous bismuth(III) nitrate. Use the standard electrode potential $E^\ominus(Bi^{3+}/Bi) = +0.32 \text{ V}$ and section 24 of the data booklet.

[2]

(c)(i)

Bismuth compounds are sometimes used in fireworks to produce special effects.

[1]

(c)(ii)

(ii) Calculate the wavelength, in nm, that corresponds to the first ionization energy of bismuth. Use sections 1, 2 and 8 of the data booklet.

[3]

(c)(iii)

(iii) Explain why the first ionization energy of bismuth is lower than that of polonium (Po), in terms of nuclear charge and electron shielding.

[2]

Question 4

EasyPaper 1A · calculator1 mark

Manganese is a transition metal known for its ability to exist in a wide range of oxidation states. Which of the following lists these manganese species in order of decreasing radius?

A. $Mn^{7+}$ , $Mn^{4+}$ , $Mn^{2+}$ , $Mn$

B. $Mn$ , $Mn^{2+}$ , $Mn^{4+}$ , $Mn^{7+}$

C. $Mn^{2+}$ , $Mn^{4+}$ , $Mn^{7+}$ , $Mn$

D. $Mn$ , $Mn^{7+}$ , $Mn^{4+}$ , $Mn^{2+}$

Question 5

MediumPaper 1A · calculator1 mark

Which option shows the correct formula and electron configuration of the species in aluminium sulfide?

A. Formula: $Al_2S_3$ ; Al species: $[Ne]$ ; S species: $[Ar]$

B. Formula: $Al_2S_3$ ; Al species: [Ne] $3s^2 3p^1$ ; S species: [Ne] $3s^2 3p^4$

C. Formula: $Al_3S_2$ ; Al species: $[Ne]$ ; S species: $[Ar]$

D. Formula: $Al_3S_2$ ; Al species: [Ne] $3s^2 3p^1$ ; S species: [Ne] $3s^2 3p^4$

Question 6

HardPaper 2 · calculator23 marks

(a)

A sample of chlorine consists of two isotopes, $^{35}Cl$ and $^{37}Cl$ .

(a) Contrast the sub-atomic structure of these two isotopes.

[1]

(b)(i)

(b) (i) The sample of chlorine is analysed in a mass spectrometer, producing a spectrum for the $Cl_2^+$ ion. The spectrum shows three peaks at m/z values of 70, 72 and 74. Explain the origin and relative heights of these three peaks, given that the abundance of $^{35}Cl$ is approximately three times that of $^{37}Cl$ .

[3]

(b)(ii)

(ii) A more precise measurement finds the composition by mass to be: $^{35}Cl$ : 75.76%, $^{37}Cl$ : 24.24%. Calculate the relative atomic mass of chlorine from this sample, giving your answer to two decimal places. (Use isotopic masses of 35.0 and 37.0 for this calculation).

[2]

(c)(i)

Magnesium chloride, $MgCl_2$ , and manganese(II) chloride, $MnCl_2$ , are two ionic compounds.

(c) (i) Deduce the type of bonding in magnesium chloride, $MgCl_2$ , using electronegativity values from section 9 of the data booklet.

[2]

(c)(ii)

(ii) Determine the lattice enthalpy of magnesium chloride, assuming the bonding is purely ionic. Use sections 9, 10 and 12 of the data booklet and the following data:

Enthalpy of formation of magnesium chloride = $-641 \text{ kJ mol}^{-1}$

[3]

(c)(iii)

(iii) Explain, with reference to electron configurations, why the ionic radii of $Mg^{2+}$ , $Mn^{2+}$ and $Cl^-$ are different. Use section 10 of the data booklet.

[3]

(c)(iv)

(iv) Predict, with a reason, which has the stronger ionic bonding, manganese(II) chloride, $MnCl_2$ , or magnesium chloride.

[2]

(d)(i)

Magnesium chloride is white, but manganese(II) chloride is pale pink.

(d) (i) State the condensed electron configuration of a manganese atom.

[1]

(d)(ii)

(ii) State the reason, in terms of electron configuration, why manganese(II) chloride is coloured.

[1]

(d)(iii)

(iii) Manganese(II) chloride absorbs light with a wavelength of approximately 530 nm. Describe why this is consistent with the observed colour of the compound. Use sections 2 and 15 of the data booklet.

[2]

(e)(i)

A copper key is to be electroplated with manganese using an aqueous solution of manganese(II) chloride as the electrolyte.

(e) (i) Deduce the half-equations for the reactions occurring at the anode (made of pure manganese) and the cathode (the copper key).

[2]

(e)(ii)

(ii) Deduce a balanced chemical equation for the reaction of fluorine gas with the aqueous chloride ions in the electrolyte.

[1]

Question 7

EasyPaper 1A · calculator1 mark

Which reaction is expected to be the most exothermic?

A. $2Li(s) + F_2(g) \rightarrow 2LiF(s)$

B. $2Li(s) + Cl_2(g) \rightarrow 2LiCl(s)$

C. $2Na(s) + F_2(g) \rightarrow 2NaF(s)$

D. $2Na(s) + Cl_2(g) \rightarrow 2NaCl(s)$

Question 8

MediumPaper 1A · calculator1 mark

Which sequence correctly lists the elements in order of decreasing melting point?

A. $Ti > Sc > Ca > K$

B. $K > Ca > Sc > Ti$

C. $Sc > Ti > Ca > K$

D. $Ti > Ca > Sc > K$

Question 9

HardPaper 2 · calculator16 marks

(a)(i)

Strontium is an alkaline earth metal in group 2 of the periodic table, used to produce the red colour in fireworks.

(a) In a sample of strontium, 10.0% of the atoms have a mass number of 86 and the remainder have a mass number of 88.

(i) Deduce the nuclear symbol of the isotope of strontium with mass number 86. Use section 6 of the data booklet.

[1]

(a)(ii)

(ii) Calculate, to two decimal places, the relative atomic mass of this sample of strontium.

[2]

(a)(iii)

(iii) Explain why the first ionization energy of strontium is greater than that of rubidium.

[2]

(b)(i)

(b) Strontium nitrate has the formula $Sr(NO_3)_2$ .

(i) The compound contains both ionic and covalent bonds. State which particles are joined by covalent bonds and which are joined by ionic bonds.

[2]

(b)(ii)

(ii) Contrast covalent and ionic bonds in terms of how the valence electrons are involved.

[1]

(b)(iii)

(iii) Write a balanced chemical equation for the formation of strontium nitrate solution from the reaction of solid strontium hydroxide with nitric acid.

[2]

(b)(iv)

(iv) Calculate the volume, in $cm^3$ , of $1.50 \text{ mol dm}^{-3}$ nitric acid required to react completely with $5.00 \text{ g}$ of solid strontium hydroxide.

[3]

(b)(v)

(v) Predict, with a reason, whether strontium oxide is acidic, basic or amphoteric.

[1]

(b)(vi)

(vi) Describe an experiment to establish the relative reactivity of strontium and zinc using the metals and aqueous solutions of their nitrates.

[2]

Question 10

EasyPaper 1A · calculator1 mark

Why is the first ionization energy of potassium (K) lower than that of sodium (Na)?

A. Potassium has a greater nuclear charge.

B. The valence electron in potassium is in a higher principal energy level.

C. Sodium has a full outer electron shell.

D. Potassium has a smaller atomic radius.

Question 11

MediumPaper 1A · calculator1 mark

Which ionic compound has the most exothermic lattice enthalpy?

A. LiF

B. LiI

C. CsF

D. CsI

Question 12

EasyPaper 1A · calculator1 mark

Which oxide reacts with both dilute sulfuric acid and aqueous potassium hydroxide?

A. MgO

B. Al₂O₃

C. P₄O₁₀

D. Na₂O

Question 13

MediumPaper 2 · calculator4 marks

(a)

The successive ionization energies for an unknown element, Z, are shown in the table below.

Ionization	Ionization Energy / kJ mol⁻¹
1st	1012
2nd	1907
3rd	2914
4th	4964
5th	6274
6th	21269

(a) Deduce the group number of element Z in the periodic table.

[1]

(b)

(b) Explain your reasoning for the answer in part (a).

[2]

(c)

[1]

Question 14

EasyPaper 1A · calculator1 mark

The first five successive ionization energies for an element are shown in the table below.

Ionization	Ionization Energy / $kJ\,mol^{-1}$
1st	786
2nd	1577
3rd	3232
4th	4356
5th	16091

To which group in the periodic table does this element belong?

A. 2

B. 13

C. 14

D. 15

Question 15

MediumPaper 2 · calculator5 marks

(a)

The first six successive ionization energies for an element, Q, are given in the table below.

Ionization Number	Ionization Energy / kJ mol⁻¹
1st	787
2nd	1577
3rd	3232
4th	4356
5th	16091
6th	19805

(a) Deduce the group number of element Q in the periodic table.

[1]

(b)

(b) Explain your answer to part (a).

[2]

(c)

[1]

(d)

(d) Write the equation, including state symbols, that represents the third ionization energy of element Q.

[1]

Question 16

EasyPaper 1A · calculator1 mark

What is the charge of the monatomic ion usually formed by the element with the following electron configuration?

$[Ar] 3d^{10} 4s^2 4p^1$

A. $1+$

B. $3-$

C. $3+$

D. $13+$

Question 17

MediumPaper 2 · calculator3 marks

(a)

Magnesium and calcium are two alkaline earth metals in the periodic table.

(a) State the full electron configuration of a magnesium atom.

[1]

(b)

(b) Explain why the first ionization energy of calcium is lower than that of magnesium.

[2]

Question 18

EasyPaper 1A · calculator1 mark

Which element is classified in the d-block of the periodic table?

A. Ba

B. Hf

C. At

D. Pm

Question 19

MediumPaper 2 · calculator6 marks

(a)

Consider the elements from the third period of the periodic table: sodium (Na), magnesium (Mg), and aluminium (Al).

(a) Explain the trend in atomic radius from sodium to aluminium.

[2]

(b)

(b) The ions $Na^+$ , $Mg^{2+}$ and $Al^{3+}$ are isoelectronic. Explain why $Al^{3+}$ has the smallest ionic radius.

[2]

(c)

(c) Compare the radius of the magnesium atom (Mg) with the radius of the magnesium ion ( $Mg^{2+}$ ), providing a reason for the difference.

[2]

Question 20

EasyPaper 2 · calculator1 mark

The formula for gallium oxide is $Ga_2O_3$ . What is the expected formula for gallium sulfide?

A. $GaS$
B. $Ga_2S$
C. $GaS_2$
D. $Ga_2S_3$

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Where marks are lost

Reaching for "human error" or "only one trial." A source of error has to be a specific step in the method, not a general apology for the result.
Joining the dots instead of drawing a curve.
Naming a chemical instead of the property that distinguishes it, or vice versa. Answering with the nearest fact that comes to mind rather than the fact the command term and stem jointly ask for is a recurring way to answer a question that was not, quite, the one asked.

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What does The periodic table: Classification of elements cover in IB Chemistry?

This topic covers the organization of elements in the periodic table and the periodic trends in their properties. The periodic table classifies elements into periods, groups, and s, p, d, f blocks, identifying metals, metalloids, and non-metals. The period number corresponds to the outer energy level, and the group number indicates the number of valence electrons.

Is The periodic table: Classification of elements SL or HL?

Both. SL and HL students study The periodic table: Classification of elements, and HL goes further: 3.1.7 Discontinuities occur in the trend of increasing first ionization energy across a period. Students explain how these discontinuities provide evidence for the existence of energy sublevels.

How do I revise The periodic table: Classification of elements for IB Chemistry?

Start from the core idea: this topic covers the organization of elements in the periodic table and the periodic trends in their properties. In the exam: trend explanations are the workhorse, usually 2 to 3 marks, and they want the causal chain: nuclear charge, shielding, atomic radius, then the property. A trend stated without a cause scores one of two. Then practise exam-style questions, easiest first, writing out every step of your working before you check it.

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The periodic table: Classification of elements: notes and practice questions

How it is examined

Guiding questions

Linking questions

Practice questions

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Question 2

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Question 7

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Question 10

Question 11

Question 12

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