Atoms & Nuclear Radiation (AQA GCSE Physics: Combined Science)

Household smoke alarms use alpha radiation sources to detect smoke.

Figure 1 shows how a smoke alarm works.

Figure 1

The smoke alarm does not sound while alpha radiation is detected by the detector. 

Explain why the alarm sounds when smoke particles enter the casing.

Why is using an alpha emitter in a smoke alarm safe to use in a house?  

Explain why the smoke alarm would not work if the alpha source were replaced by a beta or gamma source.

Figure 2 shows how the count rate from the alpha source in the smoke alarm varies with time.

Figure 2

Calculate the half life of the alpha source in the smoke alarm.

Explain why it is an advantage for the alpha emitter in the smoke alarm to have a long half life.

Of the three types of radiation, alpha (α), beta (β) and gamma (γ), which two will pass through a sheet of paper?

Which two types of radiation will be deflected by a magnetic field?

Which type of radiation has the shortest range in air?

A student suggests that the halflife of a radioactive source could be decreased by heating it in a Bunsen burner. The student thinks that this would speed up the radioactive decays, and make it decay more quickly.

Suggest why the student is wrong.

Protactinium-234 is a radioactive isotope that is often used in school science experiments. It emits beta radiation.

How is an atom of protactinium-234 different to the isotope protactinium-236?

Figure 3 shows how the count rate of a sample of protactinium-234 changes with time.

Figure 3

Use the graph to calculate the halflife of protactinium-234

Show clearly how you used the graph to obtain your answer.

Table 1 shows how the activity of a sample of plutonium-238 varies with time.

Table 1

Plot a graph of activity (y-axis) against time (x-axis).

Add a curve of best fit to your data

Use your graph to determine the halflife of plutonium-238.

Show your working.

Plutonium-238 can be used as a power source for a radioisotope thermoelectric generator (RTG).

The thermal energy produced by the plutonium-238 is converted to electrical energy to power spacecraft.

The Cassini space probe was powered with such a device.

Figure 4 shows what an RTG looks like. The radioactive sources are inside the metal container.

Figure 4

Plutonium-238 is an alpha emitter.

Explain why it is safe for scientists to handle RTG units without protective clothing.

An atom of the isotope tungsten-183 emits an alpha particle and decays into an atom of hafnium.

An alpha particle is the same as a helium nucleus. State the symbol and notation used to represent an alpha particle in nuclear equations.

How many protons and how many neutrons are there in an alpha particle?

Number of protons = _________

Number of neutrons = ________

The equation below represents the decay of tungsten-183.

Complete the equation by writing the correct number in each of the two boxes.

Atoms of the isotope iodine-128 decay by emitting a beta particle.

State the symbol and notation used to represent a beta particle in nuclear equations.

Beta decay does not cause the mass number of an atom to change.

Explain why not.

The equation representing the decay of iodine-128 to xenon is shown below.

Complete the equation by writing the correct number in each of the two boxes.

If Iodine-128 were to decay via alpha decay instead of via beta decay, it would produce a different element to xenon.

Explain why.

There is a possibility that iodine-128 can emit a gamma ray.

State the change(s) to the nucleus that would occur if iodine-128 emitted a gamma ray.

Figure 5 shows how gamma radiation can be used to irradiate food stored in a wooden box.

The radiation kills bacteria on the food.

Figure 5

Explain why gamma radiation, rather than alpha radiation is used to kill bacteria on the food.

The box has this label:

Explain why food which has been irradiated with gamma radiation is safe to eat.

Explain why foods which had been contaminated with an alpha emitter would not be safe to eat.

A sample of sodium-24 has an activity of 1400 Bq. The half-life of sodium-24 is 15 hours.

Granite is a rock which contains a radioactive isotope of uranium that decays over a long period of time. 

Explain how scientists can use this radioactivity to find the age of a piece of granite.

Higher Only

Suggest why the age of a piece of granite could not be found using a uranium isotope with a half-life of 15 hours.

Higher Only

Figure 1 shows the number of neutrons and the number of protons in some isotopes formed during successive radioactive decays.

Figure 1

Define the term isotope, and explain why some isotopes can be described as stable

Describe what happens to the number of protons and the number of neutrons when a nucleus of decays to form .

Explain why the mass number and the atomic number do not change when a gamma ray is emitted from a nucleus.

Radon-222 is radioactive. It can be represented as .

State the number of protons, the number of neutrons and the number of electrons for a neutral atom of radon-222.

Extended

Decay of a radon-222 nucleus is by α-particle emission. The element formed is polonium (Po).

Complete the equation for the decay of radon-222.

Higher Only

Radon-222 has a half-life of 3.8 days.

At a certain time, a sample contains 6.4 × 10⁶ radon nuclei.

Calculate the number of α-particles emitted by the radon nuclei in the following 7.6 days.

number of  α-particles emitted = ...........................................................

Discuss the meaning and benefits of peer-reviewed research.