Some data for argon and potassium are shown in the table.
| Element | Atomic weight | Atomic number | Chemical behaviour |
|---|---|---|---|
| Argon | 39.9 | 18 | Does not readily take part in chemical reactions |
| Potassium | 39.1 | 19 | Reacts very vigorously with water |
Explain why a scientist using Mendeleev's approach would place argon before potassium, despite the atomic weights shown.
Argon is also placed before potassium in the modern periodic table.
Explain why argon comes before potassium in the modern periodic table, and how argon can have the higher atomic weight.
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.