S3.1 The periodic table: Classification of elements
Practice exam-style IB Chemistry questions for The periodic table: Classification of elements, aligned with the syllabus and grouped by topic.
Question 1
A neutral atom has its highest-energy electron in a p sublevel. In which block of the periodic table is the element found?
A.
f-block
B.
p-block
C.
d-block
D.
s-block
Question 2
An element is in period 3 and group 16. What is the outer electron configuration of an atom of this element?
A.
4s²4p⁴
B.
2s²2p⁴
C.
3s²3p⁶
D.
3s²3p⁴
Question 3
Which element is normally classified as a metalloid?
A.
Sulfur
B.
Silicon
C.
Argon
D.
Sodium
Question 4
What are the products when potassium reacts with water?
A.
Potassium hydride and oxygen
B.
Potassium hydroxide and hydrogen
C.
Potassium hydroxide and oxygen
D.
Potassium oxide and hydrogen
Question 5
State what is meant by a period in the periodic table.
[1]
State the block associated with elements whose highest-energy electrons occupy d sublevels.
[1]
Question 6
Atomic radius decreases from sodium to chlorine. What is the main reason for this trend?
A.
Shielding by inner electrons increases greatly across the period.
B.
Nuclear charge increases while electrons are added to the same energy level.
C.
The number of occupied energy levels decreases across the period.
D.
The atoms gain electrons to form larger anions.
Question 7
Aqueous chlorine is added separately to potassium bromide and potassium iodide solutions. What is observed?
A.
No reaction with either solution
B.
Reaction with bromide only
C.
Reaction with iodide only
D.
Reaction with both bromide and iodide
Question 8
Which oxide is amphoteric?
A.
Na₂O
B.
MgO
C.
SO₃
D.
Al₂O₃
Question 9
Which property is characteristic of many transition elements because of incomplete d sublevels?
A.
Formation of only colourless ions
B.
Only one fixed oxidation state
C.
Very low melting points
D.
Formation of complex ions with ligands
Question 10
Zinc is usually not classified as a transition element. What is the reason?
A.
Its atom and common ion have full d sublevels.
B.
It is placed in the p-block.
C.
It forms no compounds.
D.
Its ions always contain unpaired d electrons.
Question 11
A transition metal complex absorbs orange light. What colour is most likely observed?
A.
Blue
B.
Yellow
C.
Red
D.
Orange
Question 12
The element selenium, Se, is in period 4 and group 16.
State the number of valence electrons in an atom of selenium.
[1]
Deduce the condensed electron configuration of selenium.
[1]
Question 13
Define first ionization energy.
[1]
State the general trend in first ionization energy down group 1.
[1]
Question 14
Write a balanced equation for the reaction of sodium with water.
[1]
State one observation that becomes more vigorous down group 1 when the metals react with water.
[1]
Question 15
Deduce the oxidation state of the underlined element in each species.
Oxygen in Na₂O₂.
[1]
Hydrogen in CaH₂.
[1]
Sulfur in SO₄²⁻.
[1]
Question 16
The graph shows atomic radius for the period 3 elements from sodium to chlorine.
Describe the trend shown.
[1]
Explain the trend using nuclear charge and shielding.
[1]
Question 17
The table gives the pH of solutions formed when several period 3 oxides are added to water.
| Oxide | Observation in water | pH of mixture |
|---|---|---|
| Na₂O | Dissolves and reacts | 13.0 |
| MgO | Slightly soluble suspension | 10.0 |
| Al₂O₃ | Insoluble; no visible change | 7.0 |
| P₄O₁₀ | Dissolves and reacts | 1.2 |
| SO₃ | Dissolves and reacts | 0.8 |
Identify one basic oxide from the data.
[1]
Identify the oxide that is most likely amphoteric.
[1]
Explain why non-metal oxides form acidic solutions in water.
[1]
Question 18
What is the oxidation state of nitrogen in NO₂⁻?
A.
+2
B.
+3
C.
+5
D.
+4
Question 19
The first ionization energy of boron is lower than that of beryllium. What is the best explanation?
A.
Boron has fewer protons than beryllium.
B.
The electron removed from boron is in a higher-energy 2p sublevel.
C.
Beryllium has more occupied energy levels than boron.
D.
Boron has a complete outer sublevel.
Question 20
What is the electron configuration of Fe³⁺?
A.
[Ar] 3d³
B.
[Ar] 4s¹ 3d⁴
C.
[Ar] 4s² 3d³
D.
[Ar] 3d⁵
Question 21
Why do many first-row transition elements form ions with different charges?
A.
Their d sublevel is always completely full.
B.
Their 4s and 3d electrons have relatively similar ionization energies.
C.
Their inner-shell electrons are removed before outer-shell electrons.
D.
Their nuclei contain variable numbers of protons.
Question 22
A complex absorbs light of wavelength 600 nm. What is the approximate frequency of this light?
A.
5.0 × 10¹⁴ s⁻¹
B.
1.8 × 10¹⁷ s⁻¹
C.
2.0 × 10¹⁴ s⁻¹
D.
6.0 × 10¹¹ s⁻¹
Question 23
A stronger ligand causes a larger splitting of d orbitals in a complex. What happens to the light absorbed?
A.
It is no longer in the visible region for any complex.
B.
It has the same wavelength but higher intensity.
C.
It has a longer wavelength and lower frequency.
D.
It has a shorter wavelength and higher frequency.
Question 24
The ionic species O²⁻, F⁻, Na⁺ and Mg²⁺ are isoelectronic.
State what is meant by isoelectronic.
[1]
Explain which of these ions has the smallest ionic radius.
[1]
Question 25
Write an equation for the reaction of calcium oxide with water.
[1]
Carbon dioxide dissolves in rainwater. Write an equation for this reaction and state its environmental significance.
[1]
Question 26
State the oxidation state of chlorine in Cl₂.
[1]
Explain why an element in its free elemental form has this oxidation state.
[1]
Question 27
The first ionization energy of oxygen is lower than that of nitrogen.
Write the outer p-electron arrangements for nitrogen and oxygen.
[1]
Explain the decrease from nitrogen to oxygen.
[1]
Question 28
State the definition of a transition element used in this course.
[1]
State one characteristic property of transition elements, other than variable oxidation state.
[1]
Question 29
Vanadium has atomic number 23.
Deduce the electron configuration of a V atom.
[1]
Deduce the electron configuration of V³⁺.
[1]
Question 30
Iron is used as a heterogeneous catalyst in some industrial reactions.
Define heterogeneous catalyst.
[1]
Explain why transition metals can act as heterogeneous catalysts.
[1]
Question 31
Define ligand.
[1]
Explain why many transition metal complexes are coloured.
[1]
Question 32
A complex absorbs light of wavelength 480 nm.
Convert this wavelength into metres.
[1]
Calculate the frequency of the absorbed light using c = 3.00 × 10⁸ m s⁻¹.
[1]
Question 33
The table shows observations when aqueous halogens are added to aqueous potassium halides.
| Halogen added | KCl(aq) | KBr(aq) | KI(aq) |
|---|---|---|---|
| Cl₂(aq) | No change; pale green solution | Reaction; orange solution forms | Reaction; brown solution forms |
| Br₂(aq) | No change; orange solution | No change; orange solution | Reaction; brown solution forms |
| I₂(aq) | No change; brown solution | No change; brown solution | No change; brown solution |
Identify the most reactive halogen in the table.
[1]
Write the ionic equation for the reaction between chlorine and bromide ions.
[1]
Explain why iodine does not react with chloride ions.
[1]
Question 34
A section of a periodic table is shown with four elements labelled W, X, Y and Z.
State which labelled element is in the same group as X.
[1]
Deduce the number of valence electrons in X if X is in group 15.
[1]
Suggest why X and the element in the same group have similar chemical properties.
[1]
Question 35
The graph shows first ionization energies for elements from lithium to neon.
Describe the overall trend across the period.
[1]
Identify the two discontinuities in the trend.
[1]
Explain one of these discontinuities in terms of the electron removed.
[1]
Question 36
The table shows successive ionization energies for a first-row transition element, M.
| Electron removed | Ionization energy / kJ mol⁻¹ |
|---|---|
| 1st | 651 |
| 2nd | 1414 |
| 3rd | 2830 |
| 4th | 4507 |
| 5th | 6299 |
| 6th | 12363 |
Suggest why several ionization energies are relatively close in value before a larger increase.
[1]
Deduce why M can form more than one oxidation state.
[1]
Question 37
The table compares several period 4 d-block elements and common ions.
| Element | Atom config. | Common ion config. | Common OS | Ion colour | Use as catalyst |
|---|---|---|---|---|---|
| Sc | [Ar] 3d1 4s2 | Sc3+: [Ar] | +3 | colourless | no common use |
| Ti | [Ar] 3d2 4s2 | Ti3+: [Ar] 3d1 | +3, +4 | purple (Ti3+) | yes |
| Fe | [Ar] 3d6 4s2 | Fe2+: [Ar] 3d6; Fe3+: [Ar] 3d5 | +2, +3 | green/brown | yes |
| Cu | [Ar] 3d10 4s1 | Cu2+: [Ar] 3d9 | +1, +2 | blue/green | yes |
| Zn | [Ar] 3d10 4s2 | Zn2+: [Ar] 3d10 | +2 | colourless | no common use |
Identify the element that should not usually be classified as a transition element.
[1]
Explain your answer using d-sublevel occupancy.
[1]
State one property in the table that supports classification of another element as a transition element.
[1]
Question 38
State the electron configuration of a copper atom.
[1]
Deduce the electron configurations of Cu⁺ and Cu²⁺.
[1]
State which of Cu⁺ or Cu²⁺ has an incomplete d sublevel.
[1]
Question 39
A cobalt complex changes colour when water ligands are replaced by chloride ions.
State two factors, other than ligand identity, that can affect the colour of a transition metal complex.
[1]
Explain how a change in ligand can lead to a change in observed colour.
[1]
Question 40
A simulation compares the reactions of lithium, sodium and potassium with water using equal-sized pieces of metal.
| Metal | First IE / kJ mol⁻¹ | Time to disappear / s | Fizzing | Flame or heat observed |
|---|---|---|---|---|
| Lithium | 520 | 82 | gentle | no flame; slight warming |
| Sodium | 496 | 31 | rapid | melts; clear warming |
| Potassium | 419 | 8 | very vigorous | lilac flame; hot solution |
Describe the trend in reactivity shown.
[1]
Explain the trend in terms of first ionization energy.
[1]
Evaluate one advantage and one limitation of using a simulation for these reactions.
[1]
Question 41
The absorption spectrum of a transition metal complex has a maximum in the yellow region of visible light.
State the colour most likely observed.
[1]
The wavelength at maximum absorption is given in the spectrum. Calculate the corresponding frequency.
[1]
Suggest one change to the complex that could shift the absorption maximum.
[1]
Explain why such a change can shift the absorption maximum.
[1]
Question 42
A calibration curve is prepared for a coloured transition metal ion using colorimetry.
Describe the relationship shown by the calibration curve.
[1]
Use the graph to determine the concentration of an unknown sample from its absorbance.
[1]
Suggest why the wavelength chosen should be strongly absorbed by the ion.
[1]
State one way to improve reliability of the concentration determination.
[1]
Question 43
Define electronegativity and state its general trend across period 3.
[1]
Explain the trends in atomic radius and electronegativity from sodium to chlorine.
[1]
Question 44
State the meaning of basic oxide, acidic oxide and amphoteric oxide.
[1]
Discuss the change in oxide properties across period 3, including equations for reactions of one basic oxide and one acidic oxide with water.
[1]
Question 45
Outline how the periodic table classifies elements into periods, groups and blocks.
[1]
Evaluate the statement: “The periodic table is a useful model, but its classifications have disputed edges.” Refer to hydrogen, metalloids or group 3 in your answer.
[1]
Question 46
Write the general balanced equation for the reaction of a group 1 metal, M, with water and state the nature of the solution formed.
[1]
Explain why the reactivity of group 1 metals increases down the group, and compare this with the trend in reactivity of group 17 elements.
[1]
Question 47
State the general trend in first ionization energy across period 2 and identify two discontinuities.
[1]
Explain how these discontinuities provide evidence for the existence of sublevels and orbitals of different energies.
[1]
Question 48
Define transition element and state why zinc is usually excluded from this classification.
[1]
Discuss how incomplete d sublevels lead to characteristic properties of transition elements. Include at least three properties.
[1]
Question 49
Deduce the electron configurations of Cr, Cr³⁺ and Mn²⁺.
[1]
Explain why first-row transition elements can form variable oxidation states, referring to electron removal and successive ionization energies.
[1]
Question 50
Explain why a transition metal complex absorbs visible light and appears coloured.
[1]
solution of a transition metal complex appears green. Evaluate how spectrophotometry could be used to determine its concentration, including the choice of wavelength and use of a calibration curve.
[1]
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