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Chemistry Paper 1
Atomic Structure
Remember: protons and neutrons in nucleus, electrons in shells.
Key Facts
- Atomic number = number of protons.
- Mass number = protons + neutrons.
Topics Covered
Atoms and Ions
What you need to know
- •Atoms have a nucleus containing protons and neutrons.
- •Electrons occupy shells around the nucleus.
- •Ions form when atoms gain or lose electrons.
Exam Tips
- Show electron shell diagrams clearly with correct numbers.
Key Terms
Isotope
Atoms of the same element with different numbers of neutrons.
Ion
A charged particle formed by gaining or losing electrons.
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Common Exam Questions
Explain why an atom becomes a positive ion.
2 markseasyChemistry Paper 1
Model Answer
It loses one or more electrons, leaving more protons than electrons.
What examiners want to see
- ✓Mention loss of electrons and net positive charge.
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