Production of Elements (Oxford AQA IGCSE Physics)

Revision Note

Production of Elements

  • Fusion reactions in stars are their source of energy

    • They produce all of the naturally occurring elements in the Universe

    • These elements may be distributed throughout the Universe by the explosion of a massive star (supernova) at the end of its life

  • For main sequence stars with a mass larger than that of our Sun:

    • Hydrogen nuclei combine in nuclear fusion reactions to produce helium nuclei, releasing lots of energy in the process

    • Stars maintain their energy output for millions of years because of the large amounts of hydrogen available

    • Once all of the hydrogen has reacted, fusion slows and the star expands becoming a red supergiant

    • Helium nuclei are then fused to form carbon

    • Further fusion processes take place in which heavier nuclei are formed such as nitrogen and oxygen

    • Heavier elements up to iron are also formed

Forces on a main sequence star

Outwards and inwards forces are balanced in a stable main sequence star, for IGCSE & GCSE Physics revision notes
The outwards and inwards forces within a star are in equilibrium. The centre red circle represents the main sequence star's core and the orange circle represents the star's outer layers
  • Once the fusion reactions inside the red supergiant cannot continue, the core of the star will collapse suddenly

  • The outer layers are blown away in a gigantic explosion 

    • This is called a supernova

    • The temperatures in the explosion are so high that the heavier nuclei can fuse to create all the naturally occurring elements in the Universe

      • All elements heavier than iron are created in supernovae

    • The explosion disperses these elements out into space

  • The early Universe contained only hydrogen because fusion is needed to create heavier nuclei

    • Before stars formed there was no fusion

Forces on a red supergiant

A main sequence star becomes a red supergiant, for IGCSE & GCSE Physics revision notes
A main sequence star will expand into a red supergiant because hydrogen is used up in the centre, so it collapses. The cooler surface expands and it becomes redder.

Last updated:

You've read 0 of your 10 free revision notes

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Ann Howell

Author: Ann Howell

Expertise: Physics Content Creator

Ann obtained her Maths and Physics degree from the University of Bath before completing her PGCE in Science and Maths teaching. She spent ten years teaching Maths and Physics to wonderful students from all around the world whilst living in China, Ethiopia and Nepal. Now based in beautiful Devon she is thrilled to be creating awesome Physics resources to make Physics more accessible and understandable for all students, no matter their schooling or background.

Caroline Carroll

Author: Caroline Carroll

Expertise: Physics Subject Lead

Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about creating high-quality resources to help students achieve their full potential.