Year 10 Science · Unit 2 · Lesson 22

The Big Bang and Formation of the Elements

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Learning Goals

Identify the odd one out in groups about nucleosynthesis and evidence.
Apply the story of element formation to interpret an abundance graph scenario.
Connect where elements form, how, and the evidence that supports the model.

Warm Up

Odd one out

Circle the item that does not belong in each group. Then explain why it doesn't fit in the answer column.

#	Group	Odd one out + reason
1	Hydrogen Helium Lithium Carbon
2	Gold Silver Uranium Helium
3	Cosmic microwave background Expansion of the Universe H and He abundance Tides on Earth
4	Big Bang nucleosynthesis Stellar nucleosynthesis Supernova Neutralisation
5	Carbon Oxygen Iron Gold

Your Turn

Scenario: the cosmic abundance of the elements

When astronomers measure ordinary matter across the Universe, they find it is about 74% hydrogen and 24% helium by mass, with every other element combined adding up to only about 2%. The Big Bang model predicted close to this ratio decades before it was measured precisely. Stars later forge heavier elements: hydrogen fuses to helium, helium to carbon and oxygen, and in massive stars fusion continues up to iron, ⁵⁶₂₆Fe.

Read the data Which two elements dominate the Universe, and roughly what fraction is everything else?
Explain the pattern Why are hydrogen and helium so much more abundant than the heavier elements?
Fusion in stars Write the sequence of fusion that builds heavier elements, from hydrogen up to iron.
Evidence Explain how this measured 74% / 24% ratio acts as evidence for the Big Bang model.
Going further Where did the gold and uranium in that final 2% actually form? Explain.

Wrap Up

In one sentence, explain why measuring how much hydrogen and helium there is in the Universe tells us something about its first few minutes.