Edexcel International A Level Chemistry
Edexcel International A Level Chemistry Ionic Bonding Exam Questions
Free Edexcel International A Level Chemistry exam questions for Ionic Bonding, with a mark scheme for every pack. Covers formation of ions, ionic bonding as electrostatic attraction, ionic radii trends, isoelectronic ions, polarisation and evidence for ions.
Ionic Bonding exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel International A Level Chemistry Ionic Bonding
Ionic bonding is a Unit 1 topic in Edexcel International A Level Chemistry that explains how and why atoms transfer electrons to form ions and what holds an ionic lattice together. You learn the definition of ionic bonding, how ionic radius changes down a group and across isoelectronic ions, and how charge and size affect the strength of the bond. The topic also introduces polarisation of anions by small, highly charged cations, which explains covalent character in some ionic compounds and is developed further in Lattice energy in Unit 4. Examiners test definitions, dot-and-cross diagrams of ionic compounds, trends in ionic radii and the experimental evidence for ions.
What you need to know
- Ionic bonding Ionic bonding is the strong electrostatic attraction between oppositely charged ions in a lattice. Metals lose electrons to form positive ions and non-metals gain electrons to form negative ions.
- Dot-and-cross diagrams Show the outer shells of the ions with square brackets and charges, for example [Na]+ and [Cl]- with a full outer shell on chloride, or MgO with 2+ and 2- ions.
- Ionic radii Ionic radius increases down a group as more shells are added. For isoelectronic ions such as N3-, O2-, F-, Na+, Mg2+ and Al3+, radius decreases as nuclear charge increases.
- Strength of ionic bonding Ionic bonding is stronger with smaller ions and higher charges, because the charge density is greater. This gives higher melting temperatures, so MgO melts at a much higher temperature than NaCl.
- Polarisation Small, highly charged cations distort the electron cloud of large anions. This polarisation gives the bond some covalent character, as in aluminium iodide.
- Evidence for ions Electrolysis of coloured ionic compounds (for example copper(II) chromate(VI) on moist filter paper) shows ions moving towards oppositely charged electrodes. Electron density maps also show separate, nearly spherical ions.
Common mistakes in Ionic Bonding
- Describing ionic bonding as transfer of electrons only. The bond is the electrostatic attraction between the ions, not the transfer itself.
- Saying ionic bonds exist between one pair of ions. The attraction acts in all directions throughout the lattice.
- Claiming Na+ is larger than Na. A positive ion is smaller than its atom because it has lost its outer shell.
- Explaining isoelectronic trends with numbers of shells. All isoelectronic ions have the same electron arrangement; it is the number of protons that changes.
- Saying the polarising power of a cation depends only on charge. It depends on charge density, so both small size and high charge matter.
Try three Ionic Bonding exam-style questions
1. Define ionic bonding. (1 mark)
Show the mark scheme answer
Strong electrostatic attraction between oppositely charged ions.
2. Explain why the ionic radius decreases from O2- to Mg2+. (2 marks)
Show the mark scheme answer
The ions are isoelectronic, with the same number of electrons in the same shells; Mg2+ has more protons so a greater nuclear charge attracts the electrons more strongly.
3. Explain why magnesium oxide has a much higher melting temperature than sodium chloride. (3 marks)
Show the mark scheme answer
Mg2+ and O2- have higher charges than Na+ and Cl-; Mg2+ is also smaller, so the ions have higher charge density; stronger electrostatic attraction between ions needs more energy to overcome.
Ionic Bonding FAQs
What does Edexcel International A Level Chemistry Ionic bonding cover?
It covers how ions form, the nature of ionic bonding, dot-and-cross diagrams, trends in ionic radii including isoelectronic ions, factors affecting bond strength, polarisation and the evidence for ions.
Which unit is Ionic bonding examined in?
Ionic bonding is part of Unit 1. Polarisation and charge density ideas come back in Unit 4 when comparing experimental and theoretical lattice energies.
How should I explain trends in melting temperature for ionic compounds?
Compare the charges and sizes of the ions, link this to charge density and the strength of the electrostatic attraction, then say more energy is needed to overcome stronger attraction.
