OCR GCSE Chemistry A C2.2 Bonding Exam Questions

About OCR GCSE Chemistry A C2.2 Bonding

C2.2 explains how the arrangement of electrons determines where elements sit in the periodic table and how atoms bond together. On the OCR Gateway Chemistry A course it is part of Topic C2 Elements, compounds and mixtures, assessed in Paper 1 (Foundation) or Paper 3 (Higher). It builds on atomic structure from C1.2 and leads directly into properties of materials in C2.3 and group trends in C4.1. Examiners frequently test Mendeleev's contribution, writing electronic structures, drawing dot and cross diagrams for ionic and covalent substances, explaining metallic bonding, and evaluating the strengths and weaknesses of different bonding models.

What you need to know

• The periodic table Mendeleev arranged elements by atomic mass but left gaps for undiscovered elements and swapped some to fit their properties. The modern table is arranged by atomic (proton) number; elements in the same group have the same number of outer shell electrons.
• Electronic structure Electrons fill shells in order: up to 2 in the first, then 8, then 8 for the first 20 elements. For example sodium is 2.8.1; the group number gives the outer electrons and the period gives the number of shells.
• Metals and non-metals Metals are on the left and centre of the periodic table and tend to lose electrons to form positive ions. Non-metals are on the right and tend to gain or share electrons.
• Ionic bonding Ionic bonding happens between metals and non-metals: electrons are transferred from the metal to the non-metal, forming oppositely charged ions held by strong electrostatic attraction. Dot and cross diagrams show the transfer and the ion charges.
• Covalent bonding Covalent bonds form between non-metal atoms when a pair of electrons is shared. Examples include H2, Cl2, H2O, NH3, CH4 and O2 (a double bond).
• Metallic bonding Metals consist of a lattice of positive ions surrounded by a sea of delocalised electrons, held together by strong electrostatic attraction. Models such as ball and stick or 2D diagrams each have limitations in how they show bonds and shape.

Common mistakes in C2.2 Bonding

• Writing that ionic bonds involve sharing electrons. Ionic bonding is the transfer of electrons and the attraction between oppositely charged ions.
• Saying Mendeleev ordered elements by atomic number. He used atomic mass, and atomic number came later.
• Drawing ions in dot and cross diagrams without square brackets and charges. Show each ion in brackets with its charge.
• Stating that a covalent bond is between two ions. A covalent bond is a shared pair of electrons between two atoms.
• Describing metallic bonding as attraction between atoms and electrons. It is attraction between positive metal ions and delocalised electrons.

Try three C2.2 Bonding exam-style questions