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First exams 2025

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Heterolytic Fission (SL IB Chemistry)

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Philippa Platt

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Heterolytic Fission

Heterolytic fission

  • Heterolytic fission is breaking a covalent bond in such a way that the more electronegative atom takes both the electrons from the bond to form a negative ion and leaves behind a positive ion

Diagram to show the process of heterolytic fission

Diagram describing how heterolytic fission on a X-Y bond results in the formation of X+ and Y- ions

Heterolytic fission forms a positive ion and a negative ion

  • In heterolytic fission, a double-headed arrow is used to show the movement of a pair of electrons
  • The resulting negative ion is an electron-rich species that can donate a pair of electrons
    • This makes the negative ion a nucleophile
  • The resulting positive ion is an electron-deficient species that can accept a pair of electrons
    • This makes the positive ion an electrophile

Heterolytic fission mechanism

Diagram showing how both electrons in a covalent bond move during heterolytic fission

  • The opposite reaction to heterolytic fission occurs when a nucleophile donates a pair of electrons to the electrophile forming a coordination bond

Reaction between a nucleophile and an electrophile forming a coordination bond

Diagram showing the movement of an electron pair from a hydroxide ion nucleophile to a proton forming water

A nucleophile ‘loves’ a positive charge and an electrophile ‘loves’ a negative charge

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    Philippa Platt

    Author: Philippa Platt

    Expertise: Chemistry

    Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener.