Periodic Patterns
Why do whole columns of the periodic table behave alike? Explore the noble gases, the alkali metals and the halogens, and learn to explain their reactivity trends with electron shells.
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Patterns in the periodic table 🧪
The periodic table arranges elements so that those with similar properties line up in **groups** (the columns). Elements in the same group have the same number of electrons in their outer shell, which is why they behave alike. This module looks at three groups with clear patterns: **Group 0** (the noble gases), **Group 1** (the alkali metals) and **Group 7** (the halogens).
Three groups to know 🔑
Each group shares an outer-shell pattern:
Why are noble gases so unreactive? 🎈
Group 0 elements barely react with anything. What best explains this?
- They already have a full outer shell of electrons
- They have no electrons at all
- They have one electron in the outer shell
- They are the most reactive of all the metals
Match each group to its feature 🔗
- Group 0, the noble gases
- Group 1, the alkali metals
- Group 7, the halogens
- Sodium dropped into water
- A full outer shell, so very unreactive
- One outer electron; reactivity increases down the group
- Seven outer electrons; reactivity decreases down the group
- Fizzes, floats and gives off hydrogen gas
Two opposite trends ↕️
Going DOWN a group, Group 1 and Group 7 change reactivity in opposite directions.
The alkali metals ✅
Select the TWO statements that are true about the Group 1 alkali metals.
- They react with water to give hydrogen and a metal hydroxide
- They become more reactive as you go down the group
- They are unreactive, like the noble gases
- They have seven electrons in their outer shell
Sodium meets water 💧
An interactive activity.
Shells and shielding ⚛️
The grade-9 explanation is all about **distance and shielding**. Going down a group, each element has an **extra electron shell**, so the outer electrons sit **further from the nucleus** and are **shielded** by the inner shells. For **Group 1**, the outer electron is **lost more easily**, so the metals get **more reactive** down the group. For **Group 7**, an outer electron is **harder to gain**, so the halogens get **less reactive** down the group.
Complete the patterns 🧱
Elements in Group 0 have a _____ outer shell, so they are very unreactive. Group 1 metals have _____ electron in their outer shell and become more reactive _____ the group. Group 7 elements are called the _____, and a more reactive halogen can _____ a less reactive one from a solution of its salt.
Spot the true statements 🖍️
An interactive activity.
Predict the reaction 🔀
An interactive activity.
Explain the trend ✍️
An interactive activity.