The periodic table is organised by electron arrangement. Once you can read the arrangement, position, trends and predicted reactions follow in a chain.
This section is part of SPM Chemistry. It connects atomic structure to the reactions you meet in later chapters.
How do the parts fit together?
The four lessons follow a single line of reasoning.
- Electron arrangement tells you the group and the period.
- Group and period, plus the number of shells, explain trends such as atomic size and reactivity.
- Evidence from reactions lets you compare groups fairly.
- The same position lets you predict how an unfamiliar element will react.
Skipping the first step is the main reason trend answers become guesswork.
One short example
An atom has the electron arrangement 2.8.5. It has three shells, so it is in period 3. It has five electrons in the outer shell, so it is in group 15.
Next, it has five outer electrons and needs three more to fill the shell, so it tends to gain electrons in reactions. One reading of the arrangement has already told you its position and its likely behaviour.
Who should start where?
Choose the lesson that matches your current gap.
| If you can do this already | Start with |
|---|---|
| Group and period get mixed up | relating electron arrangement to group and period |
| Place elements correctly but cannot explain reactivity | explaining trends using atomic structure |
| Explain trends but lose marks on experiment questions | comparing selected groups using evidence |
| Want to predict unfamiliar reactions | predicting simple reactions from periodic position |
When all four feel steady, use the periodic table practice set to mix them together.
If you would like a teacher to build the explanations with you, see online one-to-one Chemistry tuition.