Year 8 Science · Unit 2 · Lesson 12

Groups and Periods

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Learning Goals

Warm Up

Read the graph

Study the bar chart below showing the relative reactivity of Group 1 alkali metals with water, then answer the questions.

Reactivity of Group 1 Alkali Metals with Water 0 1 2 3 4 Reactivity (1–5 scale) 2 Li 3 Na 4 K 5 Rb 5+ Cs Element (top to bottom in Group 1)

Data: Adapted from Royal Society of Chemistry, periodic table reactivity data (2024)

(a) Describe the trend in reactivity as you move down Group 1 from Li to Cs.

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(b) Hydrogen (H) sits above lithium in Group 1 on some versions of the periodic table. Based on the trend in the graph, predict whether hydrogen would be more or less reactive than lithium when placed in water.

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(c) Explain why all elements in Group 1 react with water, rather than just some of them.

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Your Turn

Because… chain

Fill in the missing effects. Each step leads to the next. The shaded boxes are given, complete the empty ones.

Noble gases (Group 18) have a completely full outer electron shell
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They have no tendency to gain, lose, or share electrons with other atoms
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They do not react with other elements under normal conditions
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No compounds form naturally with noble gases
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Overall outcome, why noble gases are used in welding and in light bulbs:

Show What You Know

1. Argon (Ar) and neon (Ne) are both in Group 18. Predict how their chemical behaviour compares, and explain your reasoning using the idea of groups.

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2. Chlorine (Group 17, Period 3) and bromine (Group 17, Period 4) are both halogens. A student says "they must behave identically because they're in the same group." Agree or disagree, and explain one way their behaviour might differ.

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Wrap Up

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

HSCScience · Year 8 Science · Unit 2 · Lesson 12 · Apply Worksheet