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Dr Mark Marais

May 2025

Dr Mark Marais

May 2025

radiation is energy

released by a nucleus

to become more stable

Why Instability

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  • understand the role of the strong, weak and electromagnetic interactions
  • understand and apply conservation principles in radioactive decay
  • understand and explain nuclear instability

let’s aim to

Dr Mark Marais

May 2025

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The Fundamental Forces

Dr Mark Marais

May 2025

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Dr Mark Marais

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Dr Mark Marais

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Dr Mark Marais

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Dr Mark Marais

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Dr Mark Marais

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Dr Mark Marais

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Electromagnetic force starts dominating so positively charged protons repel each other

Alpha Decay

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May 2025

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too many neutrons to be stable

Beta Decay

too many protons to be stable

Weak force

allows protons to turn into neutrons

and vice versa through beta decay

Dr Mark Marais

May 2025

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Beta Decay

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May 2025

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Beta Decay

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May 2025

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Conservation Laws

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May 2025

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In analysing nuclear reactions, we apply conservation laws. 

Conservation Laws

  • Conservation of Nucleons
    • the total number of nucleons (protons + neutrons) is conserved

​

  • Conservation of Charge

- the sum of the charges on all the particles is conserved

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  • Conservation of Energy

- energy is conserved in nuclear reactions

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  • Conservation of Momentum

- the total momentum of the interacting particles is conserved

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May 2025

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Conservation Laws

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May 2025

Dr Mark Marais

May 2025

E.g. Apply to the following… 

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Nuclear Stability

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May 2025

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Stability

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Stability

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Stability

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Stability

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Stability

Dr Mark Marais

May 2025

In addition to the neutron/proton ratio, the actual number of neutrons and protons also determines stability.

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Stability

Dr Mark Marais

May 2025

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Stability

Dr Mark Marais

May 2025

Certain numbers of neutrons and protons will make an atom uniquely stable…

these are the…

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Stability

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Stability

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Stability

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Stability

Dr Mark Marais

May 2025

What is ‘doubly’