Nuclear Physics Flashcards
What is the average diameter of a nucleus?
10¹⁵(minus)m
What are isotopes?
Nuclei of the same element, that has the same proton number but different number of neutrons (nucleons number).
What are isorons?
Nuclei of the same element that have the same number of neutrons but different number of protons.
What are isobars?
Nuclei of the same element, that have same mass number but different number of protons.
Law of mass-energy conservation.
The total amount of mass and energy together in a system is constant.
What is mass defect?
Mass defect of a nucleus is equal to the difference between the total mass of the individual, separate nucleons and the mass of the nucleus.
Define atomic mass unit (u).
1u is defined as ¹/₁₂ of the mass of a neutral atom of carbon-12.
Conversion of u to kg.
1u = 1.6605 ×10²⁷(minus)kg
Excess mass.
Mass (in u) - nucleon number.
What is binding energy?
This is the minimum energy needed to pull a nucleus apart into it’s separate nucleons.
Why are heavy elements at risk of instability?
This is due to their large nucleus diameter. (So nuclear force is weaker making it more unstable, as it decreases with distance)
Range for an unstable nucleus.
Atomic number greater than 82.
What is nuclear force?
It is a short ranged force, that provide an attractive force stronger than any repulsive electric force. shorter than inter-atom distance and are much stronger than electrostatic forces
Define fission.
This is the process in which a massive nucleus splits to form two smaller fragments.
Define Fusion.
The process by which two very light nuclei join together to form a heavier nucleus.(occurs in sun)
Why is decay spontaneous?
- Decay of a particular nucleus isn’t affected by the presence of other nuclei.
- Decay cannot be affected by external factors such as temp and pressure. Or even chemical reactions.
Why is decay random?
- Ot is impossible to predict when a particular nucleus in a sample is going to decay.
- Each nucleus in a sample has the same chance of decaying.
What is decay constant (λ)?
The probability that an individual nucleus will decay per unit time interval.
What is the activity of a radioactive sample?
This is the rate at which nuclei decay or disintegrate. (A = -λN) or (A= N/t) (1Bq = 1s¹(minus))
Define half life.
Time taken for half the active nuclei in a sample to decay.
To find the number N that remain Undecayed over time.
N = N₀exp(-λt)
Relationships between decay constant and half life.
λ = 0.603/t