A research team makes two physical models of the same molecule. The molecule contains atoms labelled X, Y and Z.
| Information | X | Y | Z |
|---|---|---|---|
| Relative atom diameter | 1.0 | 1.5 | 2.0 |
| Sphere diameter in Model R / cm | 2.0 | 2.0 | 2.0 |
| Sphere diameter in Model S / cm | 2.0 | 3.0 | 4.0 |
In Model R, the spheres are joined by visible sticks.
In Model S, the spheres touch and no sticks are used.
A student needs to compare the relative sizes of the atoms and identify which atoms are joined by covalent bonds.
Evaluate whether Model S should replace Model R.
122 exam-style questions on OCR GCSE Chemistry 2.2 Bonding, covering 2.2.1 Metals, non-metals and the Periodic Table, 2.2.2 Types of chemical bonding and dot and cross diagrams, 2.2.3 Limitations of bonding models, and 2.2.4 Reactivity, atomic number and the modern Periodic Table. Each one has a worked solution and a mark scheme showing where the marks go.