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Describe the composition of an atom in terms of a positively charged nucleus and negatively charged electrons

Use the terms proton (atomic) number Z, nucleon (mass) number A and isotope.

Use and interpret the term nuclide and use the nuclide notation .

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Show an understanding that nuclear decay is a random and spontaneous

Show an understanding of the nature of alpha (α), beta (β) and gamma (γ) radiation.

Use equations involving nuclide notation to represent changes in the composition of the nucleus when radioactive emissions occur.

Show an understanding of background radiation.

Use the term half-life in simple calculations.

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State the meaning of nuclear fission and nuclear fusion and relate these nuclear processes with the release of energy from nuclear fuels.

Discuss the applications and hazards of radioactivity.

(i) half-life of radioactive materials,

(ii) penetrating abilities and ionising effects of radioactive emissions

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Spontaneous - Not triggered by external influences

Random - cannot predict direction (where) and or when emission take place

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Neutron in the nucleus transforms into a proton. Similar to energy, charge has to be conserved (it’s a law of nature). Hence the neutron’s transformation must be accompanied by the production of an electron to conserve charge.

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carbon-14 nucleus emits an electron (β), the total number of nucleons is unchanged but the proton number increases by 1. 

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carbon-14 nucleus emits an electron (β), the total number of nucleons is unchanged but the proton number increases by 1. 

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Background radiation refers to nuclear radiation in an environment where no radioactive source has been deliberately introduced.

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Background radiation refers to nuclear radiation in an environment where no radioactive source has been deliberately introduced.

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The half-life of a radioactive isotope is the time taken for half the nuclei in a sample of isotope to decay.

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The half-life of a radioactive isotope is the time taken for half the nuclei in a sample of isotope to decay.

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•Ionising nuclear radiation can be measured using a Geiger-Muller (GM counter).

•In one type of GM counter, the detector, counter and display are a single unit.

•In another type of GM counter as shown in Figure 17.9, a detector is connected to a counter.

•The SI unit for the amount of radioactivity is the Becquerel (Bq) which is named in honour of Henri Becquerel, a French physicist who discovered radioactivity in 1896.

•One becquerel (1 Bq) is equal to 1 disintegration per second.

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Medical imaging – The decay of radioactive nuclei often result in the emission of gamma rays and x-rays. These rays can be used to produce an image of the internal organs of a patient. Thus allowing a doctor to diagnose the illness or problem.

Destroying cancerous cells and bacteria – The high energy of gamma rays can be used to to destroy brain tumours and kill bateria in food.

Measurement of material thickness – An increase in material thickness will decrease the intensity of (α, β, γ) radiation on the exit side of the material. By measuring the intensity at the exit side, the thickness of the material in a factory production line can be tracked continuously.

Carbon dating – radioactive carbon-14 atoms are continuously being formed naturally in the atmosphere. Plants take in these atoms by photosynthesis and are eaten by animals. When living things die, the radioactive carbon-14 no longer get replenished and the concentration will slowly decay with half life of 5700 yrs. By measureing the concentration of carbon-14, we can estimate the time duration since the death of the plant or animal.

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While controlled radiation from radioactive isotopes kill cancer cells, we cannot totally avoid the damage to healthy cells.

Accidental leakage of radioactive substance can cause illness and death to living things.

Contamination of environment can disrupt the livelihood of people and animals.

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Q6. State and explain if α-particles and β-particles are radioactive.

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Q6. State and explain if α-particles and β-particles are radioactive.

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Q7. Suggest and explain why it is relatively harmless to be exposed externally to α-particles but dangerous when ingested, inhaled or absorbed through an open wound?

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Q7. Suggest and explain why it is relatively harmless to be exposed externally to α-particles but dangerous when ingested, inhaled or absorbed through an open wound?

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Are the Alpha and Beta particles radioactive ?

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Are the Alpha and Beta particles radioactive ?

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Where do the Beta electrons particles originated from?

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Where do the Beta electrons particles originated from?

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So which ones are the most dangerous ? Ionising or Penetrating ? or both? or Neither? or Something else?

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So which ones are the most dangerous ? Ionising or Penetrating ? or both? or Neither? or Something else?

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Ans: A

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Ans: A

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Ans: D

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Ans: D

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Ans: D

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Ans: C

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Ans: B

Note: Alpha particles are huge in size compared to beta particles. They lose energy as they collide and ionise air molecules,  hence cannot travel far.

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Ans: C

Note: α particles are high speed helium nuclei that are ejected by larger unstable nuclei.

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Ans: C

Note: β has different ability to pass through the two materials, hence we can tell whether the obstacle is plastic or metal. α will be blocked by both materials so we can’t tell which the 2 materials apart (similarly for γ).

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Ans: B

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Ans: D

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Ans: A

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Ans: B

Remember o deduct the background count first

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Nuclear fission is a process in which the nucleus of an atom splits (usually into two parts) and a huge amount of energy is released.

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Nuclear fission is a process in which the nucleus of an atom splits (usually into two parts) and a huge amount of energy is released.

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An example of nuclear fission reaction is when a neutron enters a large uranium nucleus to trigger the fission process.

With numerous nuclei undergoing fission processes, the large number of high speed particles released allows their kinetic energy to be used for heating water to produce steam which then drives a turbine to generate electricity.

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Nuclear fusion is a process in which two light atomic nuclei combine to form one heavier nucleus and releases a huge amount of energy. 

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Nuclear fusion is a process in which two light atomic nuclei combine to form one heavier nucleus and releases a huge amount of energy. 

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Ans: D

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Ans: C