The table gives information about the atoms of four non-metal elements, W, X, Y and Z.
| Element | Number of occupied electron shells | Number of electrons in the outer shell |
|---|---|---|
| W | 1 | 2 |
| X | 2 | 6 |
| Y | 3 | 7 |
| Z | 3 | 8 |
Two of these elements exist as single atoms and do not form molecules.
Identify the two elements. Explain your answer using the information in the table.
82 exam-style questions on AQA GCSE Chemistry 1.2 The periodic table, covering 1.2.1 The periodic table, 1.2.2 Development of the periodic table, 1.2.3 Metals and non-metals, 1.2.4 Group 0, 1.2.5 Group 1, and 1.2.6 Group 7. Each one has a worked solution and a mark scheme showing where the marks go.