Nuclear Flashcards
Almost all the alpha particles travelled through the gold film undetected. What does this imply about the structure of the atom?
The atom is mostly empty space, and the nucleus is very small compared to the size of the atom
Most of the remaining alpha particles are defected by small angles. What can be deduced about the structure of the atom from this?
The atom has a very small nucleus (relative to the size of the atom), and the nucleus is positively charged, therefore being able to repel the alpha particle.
A very small ratio of alpha particles are deflected more than 90 degrees. What can be deduced from this about the structure of the atom?
The nucleus is relatively large compared to alpha particles and contains most of the mass of the atom so that it is able to cause large deflections.
Nuclear force
The force that binds the particles into a nucleus together.
nuclide
The atomic species with a specific mass number A and proton number Z.
Isotopes
Nuclides having the same number of protons but different number of neutrons.
Radioisotopes
Radioactive isotopes
One atomic mass unit is equal to
The mass of the carbon 12 atom.
Binding energy OF A NUCLEUS is
The total energy needed to completely separate all the nucleons into its constituent protons and neutrons to infinity
Binding energy formula
(∆m)c^2
Mass defect of a nucleus is
The difference between the mass of the nucleus and the total mass of its constituent protons and neutrons.
Nuclear fission is
The splitting of a heavy nucleus into two lighter nuclei to release energy.
Nuclear fusion is
The combination of two lighter nuclei to form one heavier nucleus to release energy
Radioactive decay is
a spontaneous and random process in which an unstable nucleus disintegrates to form a more stable nucleus, emitting alpha, beta, and/or gamma radiation in the process.
What is a spontaneous process
A process that is not affected by external factors
Why is radioactive decay a random process?
It cannot be predicted which nucleus would decay first
Probability of decay per unit time of the nucleus is constant
The activity of a radioactive source
The number of disintegrations per unit time in the sample. A = (lambda*N)
The decay constant lambda is
The probability per unit time of the decay of the nucleus
The half life is
The time taken for the number of undecayed nuclei to decay to half of its original value.
Name any 2 quantities that are conserved in nuclear reactions
Total mass energy
Total momentum
Total charge (proton number, NOT NUMBER OF PROTONS)
nucleon number
State any 3 reasons why the activity of a sample is not equal to the measured count rate.
Background radiation
Daughter product is radioactive and emits radiation
Radiation emitted in all directions and absorbed in air before reaching detector
Explain how a consideration of a kinetic energy spectrum provides existence of the prediction of the existence of the neutrino.
As there is a range of kinetic energies for β-particles emitted,
for conservation of energies to be valid, apart from the daughter nucleus and the β-particle, there must be an emission of another particle such that
total energy is shared in different amounts among the daughter nucleus, β-particle and anti-neutrino.
Why must the decay of a product be stable when determining the half life from a count rate-time graph?
The decay must be stable as the emission of extra radiation adds to the existing count rate, which may cause the count rate to decrease exponentially, resulting in the half life being unable to be found from the graph
Suggest why the determination of decay constant by measuring the mass and activity of a sample can be used only for nuclides that have relatively small decay constant.
If the decay constant is small, the activity would be small and thus there would be ample data to be collected. The data sets need to be large so that an accurate value of probability can be deduced for any random event.
Explain why the random nature is radioactive decay makes it difficult to measure the decay constant to a high degree of accuracy.
To minimize the effects of randomness in decay, measurements will need to be taken in long time intervals.
For the average value calculated for each set, average may be different from true value as it is almost impossible to deduce when a nuclear would decay and what it would decay to, which makes the measurements inaccurate.
Alpha particles can be stopped by tissue paper. Suggest if this implies that alpha-emitter present no health hazards in a school laboratory.
Alpha particles are HIGHLY IONIZING. Hence, if accidentally ingested or inhaled into the body, it can cause internal damage to cells, tissue, etc.
