The Periodic Table
Year 8 ⚛️ Particles & Structure Describe the arrangement of elements in periods and groups; metal/non-metal pattern.
📊 The Periodic Table
The periodic table arranges all known elements in order of increasing atomic number. Elements with similar chemical properties are grouped in vertical groups.
Key Structure
$$\text{Period (row)} = \text{number of electron shells}$$
$$\text{Group (column)} = \text{number of outer shell electrons}$$ Elements in the same group have similar chemical properties because they have the same number of outer electrons.
🔬 Key Groups
| Group | Name | Outer electrons | Examples |
|---|---|---|---|
| 1 | Alkali metals | 1 | Li, Na, K, Rb, Cs |
| 2 | Alkaline earth metals | 2 | Mg, Ca, Ba |
| 7 (17) | Halogens | 7 | F, Cl, Br, I |
| 0 (18) | Noble gases | 8 (2 for He) | He, Ne, Ar |
📈 Trends
Properties change in predictable patterns across periods and down groups.
Down Group 1: metals get more reactive (easier to lose outer electron).
Down Group 7: halogens get less reactive (harder to gain an electron).
Across Period 3: metallic → non-metallic character; atomic radius decreases.
Down Group 7: halogens get less reactive (harder to gain an electron).
Across Period 3: metallic → non-metallic character; atomic radius decreases.
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Interactive Demonstration — The Periodic Table
Click a group or period to learn about it.
Click a region of the periodic table.
📊 Periodic Table Explorer
Look up element properties by atomic number.