The table shows data about two pairs of elements that are next to each other in the modern periodic table.
| Element | Relative atomic mass | Atomic number |
|---|---|---|
| tellurium | 127.6 | 52 |
| iodine | 126.9 | 53 |
| argon | 39.9 | 18 |
| potassium | 39.1 | 19 |
State where iodine would have been placed if Mendeleev had strictly followed the order of relative atomic mass.
Iodine has similar properties to chlorine and bromine. Explain why Mendeleev placed iodine after tellurium.
Explain why tellurium has a higher relative atomic mass than iodine even though a tellurium atom has fewer protons.
Argon was not known when Mendeleev published his table. Explain how ordering the elements by atomic number puts argon and potassium in the correct groups.
50 exam-style questions on Edexcel GCSE Chemistry 2.2 The periodic table, covering 2.2.1 Mendeleev's periodic table, 2.2.2 Periods, groups, metals and non-metals, and 2.2.3 Electronic configuration and position in the periodic table. Each one has a worked solution and a mark scheme showing where the marks go.