Lesson 15, Topic 1
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Nuclear Decay

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Rules for nuclear equations

  1. Conservation of charge – Sum of atomic numbers must be equal for both sides.
  2. Conservation of mass number – Sum of mass numbers must be equal for both sides.

Particles of Nuclear Reactions

ParticleAtomic NumberMass NumberSymbol
Alpha particle24[katex]_2^4He[/katex]
Anti-neutrino00[katex]\overline\nu[/katex]
Beta particle (electron)-10[katex]_{-1}^0e[/katex]
Deuteron (deuterium nucleus)12[katex]_1^2H[/katex]
Gamma ray00[katex]\gamma[/katex]
Neutron01[katex]_0^1n[/katex]
Neutrino00[katex]\nu[/katex]
Positron10[katex]_{+1}^0e[/katex]
Proton11[katex]_1^1H[/katex]

Types of Decay

AlphaBeta MinusGamma
[katex]^A_Z \text X \rightarrow ^{A-4}_{Z-2} \text X + ^4_2 \text{He}[/katex]

Emits alpha particle
[katex]^A_Z \text X \rightarrow ^{\space \space \space \space \space A}_{Z+1} \text X + {}^{\space \space \space 0}_{-1} e \space + ^0_0 \overline{\nu}[/katex]

Emits electron* and antineutrino**
[katex]^A_Z X^* \rightarrow {}^A_ZX + \gamma[/katex]

Emits gamma ray
A few cm of air
Absorption
Around 1m of air
Absorption
Many cm of lead
Absorption
Strong
Ionising Power
Medium
Ionising Power
Weak
Ionising Power

To conserve mass-energy, the mass deficit transforms to kinetic energy in expelled particles.

A Note on Beta Decay

*An electron is emitted in beta minus decay, while an anti-electron (positron) is emitted in beta plus decay.

**In beta minus decay, a neutrino is emitted.

  • β decay = neutron transforming into a proton
  • β+ decay = proton transforming into a neutron