CCEA A Level Chemistry
CCEA A Level Chemistry 1.3 Bonding Exam Questions
Free CCEA A Level Chemistry revision for 1.3 Bonding: what you need to know, common mistakes and exam-style questions with answers. Covers ionic, covalent, co-ordinate and metallic bonding, dot and cross diagrams, the octet rule, electronegativity and bond polarity.
Practise 1.3 Bonding with past papers
Once you have learnt this topic, find the 1.3 Bonding questions in real CCEA A Level Chemistry past papers and mark them with the mark scheme. Doing lots of real questions is the quickest way to learn how examiners ask about each idea.
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About CCEA A Level Chemistry 1.3 Bonding
Bonding is section 1.3 of Unit AS 1. You need dot and cross diagrams for ionic compounds of Groups I, II, VI and VII, covalent molecules with single, double and triple bonds and lone pairs, and co-ordinate (dative) bonds such as in the ammonium ion. CCEA also asks about the octet rule and its limitations, using BeCl2 and BF3 as examples of electron deficient molecules. You must explain electronegativity trends, show bond polarity with partial charges, and describe metallic bonding as positive ions in a sea of delocalised electrons. This leads directly into intermolecular forces (1.4), structure (1.5) and shapes (1.6).
What you need to know
- Ionic bonding Electrostatic attraction between oppositely charged ions formed by electron transfer, for example Na+ and Cl-, or Mg2+ and O2-. Show outer electrons only, with charges in brackets.
- Covalent bonding A shared pair of electrons between two atoms. Double and triple bonds share two and three pairs. Lone pairs are non-bonding pairs on an atom.
- Co-ordinate bonding Both electrons in the shared pair come from one atom, for example the lone pair on N in NH3 bonding to H+ to form NH4+. Once formed it is identical to the other N-H bonds.
- Octet rule limits BeCl2 has only four electrons around Be and BF3 has only six around B, so they are electron deficient. Some elements in Period 3 can expand the octet, for example SF6.
- Electronegativity and polarity Electronegativity is the ability of an atom to attract the bonding pair of electrons in a covalent bond. It increases across a period and up a group; fluorine is the most electronegative. Unequal sharing gives a polar bond shown with delta+ and delta-.
- Metallic bonding A lattice of positive metal ions attracted to a sea of delocalised electrons.
Common mistakes in 1.3 Bonding
- Defining electronegativity as attracting an electron. It is attracting the bonding pair of electrons in a covalent bond.
- Drawing ionic compounds with shared electrons. Show transfer, with square brackets and charges on each ion.
- Saying the co-ordinate bond in NH4+ is different in length or strength. All four N-H bonds are identical once formed.
- Calling a metallic bond attraction between atoms. It is attraction between positive ions and delocalised electrons.
- Saying BF3 obeys the octet rule. Boron has only six electrons in its outer shell.
Try three 1.3 Bonding exam-style questions
1. Draw a dot and cross diagram for magnesium oxide, showing outer electrons only. (2 marks)
Show the mark scheme answer
[Mg]2+ with no outer electrons (or full shell shown); [O]2- with eight outer electrons, two of them shown as crosses from Mg.
2. Explain how ammonia forms a co-ordinate bond with a hydrogen ion. (2 marks)
Show the mark scheme answer
Nitrogen has a lone pair of electrons; it donates both electrons to the H+ ion to form a shared pair (dative bond), giving NH4+.
3. Explain why the H-F bond is polar. (2 marks)
Show the mark scheme answer
Fluorine is more electronegative than hydrogen; the bonding pair is pulled towards F, making F delta- and H delta+.
1.3 Bonding FAQs
What does CCEA A Level Chemistry 1.3 Bonding cover?
It covers ionic, covalent, co-ordinate and metallic bonding, the octet rule and its limitations, electronegativity and bond polarity.
Which unit is 1.3 Bonding examined in?
It is examined in Unit AS 1: Basic Concepts in Physical and Inorganic Chemistry, a 1 hour 30 minute paper with a multiple-choice section and structured questions. Related practical skills can also be assessed in Unit AS 3.
Which examples break the octet rule for CCEA?
Learn BeCl2 and BF3 as electron deficient molecules, and be ready to explain why they do not have eight electrons around the central atom.
