Chapter 2 Flashcards
(18 cards)
What is radioactivity?
Spontaneous emission of radiation due to unstable nuclei.
Radioactivity is a key concept in nuclear physics, indicating the instability of certain atomic nuclei.
What determines the stability of nuclei?
Neutron-to-proton (n/p) ratio.
A stable nucleus typically has a balanced n/p ratio, while instability often leads to radioactivity.
List the types of radioactive decay.
- Alpha (α)
- Beta (β)
- Gamma (γ)
- Electron Capture
- Internal Conversion
Each decay type has distinct characteristics and effects on the nucleus.
What is the decay equation?
N = N_0 e^{-lambda t}
This equation describes the number of undecayed nuclei over time.
How is activity (A) defined in radioactive decay?
A = A_0 e^{-lambda t}
Activity represents the rate of decay of radioactive material.
What is half-life (T₁/₂)?
T_{1/2} = rac{0.693}{lambda}
Half-life is the time required for half of the radioactive nuclei in a sample to decay.
What is the relationship between mean life (Tₐ) and half-life (T₁/₂)?
T_a = rac{1}{lambda} = 1.44 T_{1/2}
Mean life is the average lifetime of a radioactive particle before it decays.
What occurs during alpha (α) decay?
Heavy nuclei emit helium nucleus (²He⁴), reducing atomic number (Z) by 2 & mass (A) by 4.
An example is {}^{226}Ra
ightarrow {}^{222}Rn + α.
Describe beta (β) decay.
- β⁻ (Negatron emission): Neutron → Proton + Electron + Antineutrino
- β⁺ (Positron emission): Proton → Neutron + Positron + Neutrino
An example of β⁻ decay is {}^{32}P
ightarrow {}^{32}S + β^-.
What is gamma (γ) emission?
Nucleus releases excess energy without changing Z or A, usually following α or β decay.
Gamma emissions are commonly used in radiation therapy.
What happens during electron capture (K-Capture)?
Proton absorbs an electron → Converts into a neutron.
An example is {}^{11}C + e^-
ightarrow {}^{11}B + ν.
Define internal conversion.
Excited nucleus transfers energy to an orbital electron, ejecting it.
Internal conversion competes with gamma emission.
What is secular equilibrium?
T₁/₂ (Parent) ≫ T₁/₂ (Daughter)
An example includes Radium-226 and Radon-222.
What is transient equilibrium?
T₁/₂ (Parent) > T₁/₂ (Daughter)
An example includes Molybdenum-99 and Technetium-99m.
Describe the (α, p) reaction.
Alpha particle hits a nucleus → Proton emitted.
This reaction is significant in nuclear physics and applications.
What occurs during the (n, γ) reaction?
Neutron absorption → Gamma emission.
This reaction is used in neutron activation.
What is fission?
Heavy nucleus splits.
Fission is utilized in nuclear reactors.
What is fusion?
Lighter nuclei combine.
Fusion occurs in stars and is a potential source of energy.
