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Changes in Number of Subatomic Particles

Chemistry: Edexcel IGCSE, topic 6.1.2

Changes in Number of Subatomic Particles

When an atom gains or loses electrons, the nucleus does not change. This means the atomic mass and the atomic number stay the same.

Cations

Cations

  • If an ion is positive, it has fewer electrons than protons.
  • A 1+ charge means 1 less electron than proton (e.g. Na+).
  • A 2+ charge means 2 less electrons than protons (Ca2+).
Anions

Anions

  • If an ion is negative, it has more electrons than protons.
  • A 1- charge means 1 more electron than proton (e.g. Cl-).
  • A 2- charge means 2 more electrons than protons (O2-).

Test yourself on Changes in Number of Subatomic Particles

  • How many more protons than electrons does an Na+ ion have?

  • Which of these are true of cations and anions?

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