Year 8 Science · Unit 2 · Lesson 14

Patterns in the Periodic Table

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Learning Goals

Warm Up

Because… chain

Fill in the missing effects. Each cause leads to the next step in the chain. The first and third boxes are given, complete the second and fourth.

Elements in Group 1 share a similar outer electron arrangement.
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Each Group 1 element reacts with water to produce hydrogen gas and a metal hydroxide.
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Overall outcome: knowing one Group 1 element's behaviour lets you predict all others because…

Your Turn

Read the graph

The graph below shows the melting points of Group 1 alkali metals from lithium (top of group) to caesium (bottom). Study the graph, then answer the questions.

Melting Points of Group 1 Alkali Metals 200 150 100 50 0 Melting point (°C) 181°C 98°C 63°C 39°C 28°C Li Na K Rb Cs Element (down Group 1)

Data: CRC Handbook of Chemistry and Physics (adapted for educational use)

(a) Describe the trend in melting point as you go down Group 1 from lithium to caesium.

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(b) Francium (Fr) sits below caesium in Group 1. Using the trend in the graph, predict the approximate melting point of francium. Show your reasoning.

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(c) What does the decreasing melting point suggest about the strength of the forces holding alkali metal atoms together as you go down the group?

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Show What You Know

1. Chlorine (Cl) and bromine (Br) are both in Group 17. Chlorine reacts more vigorously with iron than bromine does. Use this information and the group pattern to predict what you would expect when iodine (I, below Br) reacts with iron.

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2. A chemist discovers a new element that belongs to Group 18 (the noble gases). Without doing any experiments, what can the chemist predict about its reactivity? Explain why the periodic table makes this prediction possible.

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Wrap Up

In one sentence, what was the main idea of this lesson?

HSCScience · Year 8 Science · Unit 2 · Lesson 14 · Apply Worksheet