The Periodic Table
Read groups and periods and use the table to predict properties.
The periodic table arranges elements by atomic number.
- Explain how groups and periods are arranged.
- Locate metals, non-metals and noble gases.
- Predict properties from group position.
Rows and Columns
Periods are horizontal rows; the period number equals the number of electron shells. Groups are vertical columns; elements in a group have the same number of outer electrons and similar properties.
Key Groups
- Group 1 — alkali metals: soft, reactive, one outer electron.
- Group 2 — alkaline earth metals.
- Group 7 — halogens: reactive non-metals.
- Group 0 — noble gases: full outer shell, very unreactive.
Metals and Non-metals
Most elements on the left and centre are metals; most on the right are non-metals. A staircase line separates them, with metalloids such as silicon along the border.
Sodium is in Group 1, Period 3: three shells and one outer electron. It forms a 1+ ion.
Chlorine is in Group 7, Period 3: seven outer electrons. It forms a 1− ion.
Practice
- How many electron shells does an element in Period 4 have?
- Why are noble gases unreactive?
- Predict whether potassium or lithium is more reactive. Explain.
Recap
The periodic table groups elements by atomic number. Group number relates to outer electrons and therefore to chemical behaviour.
AI Notes
Get AI-powered summaries, key points, and quick revision notes for this lesson — available with Premium.
Unlock AI NotesContents
Atomic Structure and Bonding
0/3 lessons completed