A LevelPhysicsCambridge (CIE)Revision Notes23. Nuclear PhysicsMass Defect & Nuclear Binding EnergyNuclear Equations

Nuclear Equations (Cambridge (CIE) A Level Physics): Revision Note

Exam code: 9702

Leander Oates

Written by: Leander Oates

Reviewed by: Caroline Carroll

Updated on

Representing simple nuclear reactions

  • A nucleus can be described using XZA notation

AZX Notation, downloadable AS & A Level Physics revision notes

XZA notation is used to describe the constituents of a nucleus

  • The top number A represents the nucleon number or the mass number

    • Nucleon number (A) = total number of protons and neutrons in the nucleus

  • The lower number Z represents the proton or atomic number

    • Proton number (Z) = total number of protons in the nucleus

Worked Example

When a neutron is captured by a uranium-235 nucleus, the outcome may be represented by the nuclear equation:

U92235 + n01 → Mo4295 + La57139 + xn01 + 7e−10

Determine the value of x.

Answer: 

Step 1: Balance the nucleon numbers (the top number)

235 + 1 = 95 + 139 + x(1) + 7(0)

Step 2: Rearrange to find the value of x

x = 235 + 1 − 95 − 139 = 2

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Author
Reviewer
Leander Oates

Author: Leander Oates

Expertise: Development Editor

Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.

Caroline Carroll

Reviewer: Caroline Carroll

Expertise: Head of Content Delivery

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 delivering high-quality resources to help students achieve their full potential.