Nuclear

Question 1

Almost all the alpha particles travelled through the gold film undetected. What does this imply about the structure of the atom?

Answer 1

The atom is mostly empty space, and the nucleus is very small compared to the size of the atom

Question 2

Most of the remaining alpha particles are defected by small angles. What can be deduced about the structure of the atom from this?

Answer 2

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.

Question 3

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?

Answer 3

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.

Question 4

Nuclear force

Answer 4

The force that binds the particles into a nucleus together.

Question 5

nuclide

Answer 5

The atomic species with a specific mass number A and proton number Z.

Question 6

Isotopes

Answer 6

Nuclides having the same number of protons but different number of neutrons.

Question 7

Radioisotopes

Answer 7

Radioactive isotopes

Question 8

One atomic mass unit is equal to

Answer 8

The mass of the carbon 12 atom.

Question 9

Binding energy OF A NUCLEUS is

Answer 9

The total energy needed to completely separate all the nucleons into its constituent protons and neutrons to infinity

Question 10

Binding energy formula

Answer 10

(∆m)c^2

Question 11

Mass defect of a nucleus is

Answer 11

The difference between the mass of the nucleus and the total mass of its constituent protons and neutrons.

Question 12

Nuclear fission is

Answer 12

The splitting of a heavy nucleus into two lighter nuclei to release energy.

Question 13

Nuclear fusion is

Answer 13

The combination of two lighter nuclei to form one heavier nucleus to release energy

Question 14

Radioactive decay is

Answer 14

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.

Question 15

What is a spontaneous process

Answer 15

A process that is not affected by external factors

Question 16

Why is radioactive decay a random process?

Answer 16

It cannot be predicted which nucleus would decay first

Probability of decay per unit time of the nucleus is constant

Question 17

The activity of a radioactive source

Answer 17

The number of disintegrations per unit time in the sample. A = (lambda*N)

Question 18

The decay constant lambda is

Answer 18

The probability per unit time of the decay of the nucleus

Question 19

The half life is

Answer 19

The time taken for the number of undecayed nuclei to decay to half of its original value.

Question 20

Name any 2 quantities that are conserved in nuclear reactions

Answer 20

Total mass energy
Total momentum
Total charge (proton number, NOT NUMBER OF PROTONS)
nucleon number

Question 21

State any 3 reasons why the activity of a sample is not equal to the measured count rate.

Answer 21

Background radiation
Daughter product is radioactive and emits radiation
Radiation emitted in all directions and absorbed in air before reaching detector

Question 22

Explain how a consideration of a kinetic energy spectrum provides existence of the prediction of the existence of the neutrino.

Answer 22

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.

Question 23

Why must the decay of a product be stable when determining the half life from a count rate-time graph?

Answer 23

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

Question 24

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.

Answer 24

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.

Question 25

Explain why the random nature is radioactive decay makes it difficult to measure the decay constant to a high degree of accuracy.

Answer 25

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.

Question 26

Alpha particles can be stopped by tissue paper. Suggest if this implies that alpha-emitter present no health hazards in a school laboratory.

Answer 26

Alpha particles are HIGHLY IONIZING. Hence, if accidentally ingested or inhaled into the body, it can cause internal damage to cells, tissue, etc.