The structure of an atom

Figure 5 shows a diagram of a helium atom.

Complete the table for particles G and H, as shown in Figure 5.

An atom of beryllium has the symbol

Be 9 4

The beryllium atom has 4 protons.

Determine the number of neutrons in this atom.

Determine the number of electrons in this atom.

Which of these is the unit for the activity of a radioactive isotope?

The isotope nitrogen-13 (N-13) has a half-life of 10 minutes.

A sample of N-13 has an initial mass of 120 g.

Calculate the mass of N-13 that remains after 30 minutes.

mass remaining =_........

Figure 6 is a diagram representing an atom.

Write the names of the particles X, Y and Z on the lines next to each letter in Figure 6.

The nucleus of a different atom emits a gamma ray.

What happens to the number of particles in the nucleus?

A teacher demonstrates a radioactivity experiment to a class of students.

The teacher places a radioactive source in front of a radiation detector.

State one safety precaution the teacher should take.

The teacher uses the detector to measure the activity of the source several times.

Figure 7 shows the results.

The teacher tells the class that radioactive decay is random.

State how the data in Figure 7 supports this statement.

Calculate the mean of the four measurements in Figure 7.

mean =_........ Bq

The teacher moves the radiation detector to different distances from the radioactive source.

The teacher determines the mean detector reading at each distance from the source.

The teacher plots the results on graph paper, as shown in Figure 8.

The source emits alpha radiation only.

Explain how the graph in Figure 8 shows that the source only emits alpha radiation.

Give a reason why the mean detector reading in Figure 8 does not fall to zero in this experiment.

Ultraviolet (UV) waves from the Sun travel towards the Earth.

Ultraviolet waves can be grouped by wavelength.

The three groups of wavelengths are UVA, UVB and UVC.

Figure 4 shows, for each group,

• the wavelength range

• the effect of the Earth’s atmosphere on each type of UV wave.

Explain why UVC is potentially the most dangerous ultraviolet radiation but does not cause harm to people.

The speed of electromagnetic radiation is 3 00. 10⁸ m/s.

Calculate the frequency of the shortest wavelength of UVB radiation.

frequency =_........ Hz

UV radiation of wavelength 365 nm is used to detect forged banknotes.

In a genuine banknote there are marks that cannot be seen using visible light. These marks can be seen using UV radiation.

Explain why the marks can be seen when the UV radiation shines on the banknote.

Your answer should refer to the energy of electrons in atoms.

You may draw a diagram to help with your answer.

An atom has a central nucleus containing neutrons and protons.

Electrons orbit the nucleus.

Which row of the table gives the relative mass and charge of a proton?

An atom has a radius of 1.0 × 10^–10m.

A nucleus has a radius of 1.0 × 10^–15m.

Calculate the ratio of the radius of the atom to the radius of the nucleus.

ratio of radius of atom to radius of nucleus =_........

Explain why an atom has no charge overall.

State the number of protons in one atom of carbon‑14.

number of protons =_........

State the number of neutrons in one atom of carbon‑14.

number of neutrons =_........

Figure 4 shows a graph for the decay of the radioactive isotope carbon‑14.

Use the graph to estimate the half‑life of carbon‑14.

half‑life =_........ years

Figure 8 is the symbol for a nucleus of americium-241.

Figure 8

Americium-241 is a radioactive isotope of americium.

Americium-241 decays by emitting alpha (α) particles.

Which of these is the symbol for another radioactive isotope of americium?

Which of these is the approximate maximum distance that alpha particles can travel in air at normal atmospheric pressure?

Complete the equation in Figure 9 for americium-241 decaying into neptunium (Np).

Figure 9

The activity of a radioactive source is measured as 128 Bq.

This is shown as a point on the graph in Figure 10.

The half-life of this radioactive source is 17 s.

Use this information to plot three more points on the graph grid in Figure 10 to show how the activity of the source changes with time.

Describe what happens in the nucleus of an atom when a positron is emitted.

Figure 7 shows a safety sign on the door of a laboratory where radioactive materials are used.

State one way that radioactivity can be dangerous to humans.

State one piece of equipment that can be used to measure radioactivity.

Alpha (α) radiation and ultraviolet (UV) radiation are ionising radiations.

Give two other ionising radiations.

A sample of a radioactive isotope has a mass of 520 g.

The half‑life of the radioactive isotope is 18 days.

Calculate the mass of the original radioactive isotope remaining after 18 days.

mass after 18 days_........ g

Calculate the mass of the original radioactive isotope remaining after 54 days.

mass after 54 days_........ g

Rutherford devised an experiment to fire alpha particles at thin gold foil.

It was found that alpha particles were scattered by the gold foil.

The gold foil was about 4.010^–7m thick.

A gold atom has a diameter of about 0.15 nm.

Estimate how many gold atoms would fit across this thickness of gold foil.

number of atoms =_........

The apparatus that was used in the experiment is shown in Figure 6.

The number of particles detected at each angle in a given time is shown on the graph in Figure 7.

Use information from the graph.

Estimate the ratio of the number of particles scattered through 5 to the number of particles scattered through 100.

ratio =_........

Explain how the difference in the number of particles scattered at different angles gives evidence for the current model of the structure of the atom.

Describe how the students could use the apparatus to model the scattering of alpha particles.

Give one limitation of this model.

This question is about waves in the electromagnetic (e.m.) spectrum.

The potential danger associated with the waves of the e.m. spectrum increases as

A microwave oven uses waves of frequency 2.45 GHz.

Calculate the wavelength of the microwaves.

wavelength =_........ m

The microwave oven is 55% efficient and transfers 42 000 J of energy to some food when it is heated.

Calculate the total amount of energy that must be supplied to the oven.

energy supplied to oven =_........ J

*(c) X-rays and radio waves are part of the electromagnetic spectrum and have different uses.

These radiations are produced in different ways.

X-rays are emitted when electrons within an atom go through energy changes.

Radiowaves are produced by electrons in circuits.

Compare X-rays with radio waves.

Your answer should refer to

• the uses of both types of radiation

• the different ways that electrons are involved in producing X-rays and radio waves.

This question is about radioactivity.

Alpha (α), beta (β) and gamma (γ) are three types of radioactive emissions.

Which statement describes all of these radioactive emissions?

Fluorine-19 is a stable isotope of the element fluorine.

The element fluorine also has several radioactive isotopes.

Describe one similarity and one difference between the numbers of particles in one nucleus of fluorine-19 and one nucleus of a radioactive isotope of fluorine.

similarity_........

Figure 10 shows a Geiger–Muller (G–M) tube attached to a counter. The G–M tube is used to measure the activity of a source of beta (β) radiation. There is an aluminium sheet between the beta source and the G–M tube. The counter is switched on and after 1 minute shows a count of 268.

The aluminium sheet is taken away. The counter is reset to zero and then switched on again. A new count is taken for 1 minute.

Explain why the new count is greater than 268.

The beta source is then also taken away. The counter is reset to zero and switched on again. A new count is taken for 1 minute.

Give a reason why there would now be a reading on the counter.

State the SI unit for the activity of a radioactive source.

*(d) Exposing people to radioactive sources can be dangerous.

Describe the dangers of exposure to radioactive sources and what can be done to protect hospital staff when they are working with radioactive sources.

Equations

This question is about radioactivity.

Alpha (α), beta (β) and gamma (γ) are three types of radioactive emissions.

Which statement describes all of these radioactive emissions?

Fluorine-19 is a stable isotope of the element fluorine.

The element fluorine also has several radioactive isotopes.

Describe one similarity and one difference between the numbers of particles in one nucleus of fluorine-19 and one nucleus of a radioactive isotope of fluorine.

similarity_........

Figure 3 shows a Geiger–Muller (G–M) tube attached to a counter. The G–M tube is used to measure the activity of a source of beta (β) radiation. There is an aluminium sheet between the beta source and the G–M tube. The counter is switched on and after 1 minute shows a count of 268.

The aluminium sheet is taken away. The counter is reset to zero and then switched on again. A new count is taken for 1 minute.

Explain why the new count is greater than 268.

The beta source is then also taken away. The counter is reset to zero and switched on again. A new count is taken for 1 minute.

Give a reason why there would now be a reading on the counter.

State the SI unit for the activity of a radioactive source.

Radium-223 is a radioactive substance.

Radium-223 is an alpha emitter.

The half-life of radium-223 is 11 days.

A radioactive source contains 1.7 × 10²³ nuclei of radium-223.

Calculate the number of radium-223 nuclei remaining in the source after a time of 33 days.

number of radium-223 nuclei remaining =_........

Which of these describes isotopes of an element?

Figure 7 represents a decay that can happen inside the nucleus of an atom.

Which decay is represented in Figure 7?

The half-life of cobalt-60 is 5 years.

A school cobalt source had an activity of 38.5 kBq in the year 2000.

Estimate the activity of this source in the year 2020.

activity =_........ kBq

Explain what can happen to the body if a person has a prolonged exposure to gamma rays.

Calculate the average count rate, in counts / s, from the graph.

Show your working on the graph.

average count rate =_........ counts / s

The student says that the experiment must have been done carelessly because the data seemed quite scattered away from the best fit line.

The teacher claims such results should be expected in radioactivity experiments.

Justify the teacher’s claim.

Carbon-13 and carbon-14 are isotopes of carbon.

Nuclei of carbon-13 and carbon-14 can be represented by these symbols

13 14

Complete the table for an atom of carbon-13 and an atom of carbon-14.

State the name of an instrument that can be used to measure radioactivity.

State two sources of background radiation.

Carbon-14 is radioactive and has a half-life of 5 700 years.

The number of radioactive carbon-14 atoms in a very old piece of wood is found to have decreased from 1 000 000 to 125 000.

Determine the age of the piece of wood.

age of wood =_........ years

Carbon-14 decays into nitrogen-14.

The symbol for nitrogen-14 is¹⁴₇N

Explain what happens in a carbon-14 nucleus when it decays to a nitrogen-14 nucleus.

Figure 1 gives the names of three atomic particles and some descriptions of the charge on the particles and their position in the atom.

Draw one straight line from each atomic particle to its correct description.

Figure 2 shows the junction of three wires, F, G and H, in a circuit. The current in wire F is 6.0 A. The current in wire G is 3.5 A.

Calculate the current in wire H.

current in wire H =_........ A

A wire in a circuit carries a current of 0.9 A. Calculate the quantity of charge that flows through the wire in 50 s.

State the unit of charge with your answer.

Use the equation

charge = current × time

quantity of charge =_........ unit_........