# A doctor is explaining to a medical student how the human body is made from a small number of chemical elements. The doctor states that just six non-metallic elements account for over 99% of the mass of the human body, and that the most abundant element in the universe is also found in the body. Explain which elements make up most of the human body, how these elements were formed, and why carbon is particularly important for living organisms.

> OCR A-Level Chemistry B: Salters (H433) — EL Elements of life · Explain · 5 marks

> Just six non-metallic elements account for over 99% of the mass of the human body. The most abundant element in the universe is also found in living organisms.

## Mark scheme (5 marks)

1. Identifies hydrogen, oxygen, carbon, nitrogen, phosphorus, and sulfur as the six main elements in the human body (accept any four correctly named for this mark)
2. States that hydrogen was formed in the Big Bang
3. States that the other elements (heavier than hydrogen) were formed by nuclear fusion in stars
4. States that these elements were distributed across the universe when stars exploded (supernovae) and eventually became part of the Earth and living organisms
5. Explains that carbon can form four bonds and bond to itself to make long chains or rings, allowing a huge variety of complex molecules needed for life

## Key terms

- [non-metallic elements](https://www.gradenine.co.uk/glossary/non-metallic-elements)

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-doctor-is-explaining-to-a-00cd53a8) · Published by Druglandscape Ltd.