The structure of an atom

Uranium‑239 is an isotope of the element uranium.

State what is meant by the term isotopes.

Uranium‑239 can be represented using the symbol

Protons are one type of particle found in the nucleus of an atom.

How many protons are in the nucleus of an atom of uranium‑239?

Give the name of the other particle found in the nucleus of an atom of uranium‑239.

Uranium‑239 is radioactive and decays by beta emission.

Uranium‑239 has a half‑life of 23 minutes.

A sample of uranium‑239 has an initial mass of 60 g.

Calculate the mass of uranium‑239 remaining after 46 minutes.

When uranium‑239 undergoes beta decay, an isotope of the element neptunium, Np, is produced.

Which of these is the correct symbol for the neptunium nucleus produced in the beta decay of uranium‑239?

This question is about radioactivity.

The nucleus of an atom of carbon has 6 protons and 8 neutrons.

Which row of the table shows the nucleus of an atom that is a different isotope of carbon?

Which type of radiation is a high-energy electron?

A nucleus emits radiation. This causes the mass number to decrease by one. The atomic number stays the same.

Which type of radiation does the nucleus emit?

The nucleus of an isotope of uranium can be represented using this symbol.

The nucleus forms part of a positively charged ion.

How many electrons could be in this ion?

A radioactive isotope has an initial activity of 400 Bq.

The half-life of the isotope is 8 hours.

What is the activity of the isotope after 16 hours?

This question is about radioactive isotopes used for medical imaging.

How many neutrons are in the nucleus of an atom of iodine-131?

Iodine-131 is radioactive and decays with a half-life of 8 days.

State what is meant by the term half-life.

The cross () on the graph shows the initial number of atoms in a sample of iodine-131.

Draw three more crosses () on the graph to show how the number of atoms of iodine-131 in the sample changes during three half-lives.

[iodine-131 half-life = 8 days]

Use a curve of best fit on the graph to estimate the time taken for the number of atoms in the sample to decrease to 5000.

When iodine-131 decays, it emits beta radiation and gamma radiation.

A patient swallows a tablet containing iodine-131. The radiation emitted can be detected outside the body.

State the name of a piece of equipment that can detect the radiation emitted by iodine-131.

Give a reason why gamma radiation is more likely to be detected outside the body than beta radiation.

Technetium-99m is another radioactive isotope.

Iodine-131 and technetium-99m are both used as medical tracers. Medical tracers use radiation detected outside the body to diagnose illnesses.

The table gives information about some of the properties of iodine-131 and technetium-99m when they undergo radioactive decay.

Explain why technetium-99m is likely to be safer than iodine-131 when used as a medical tracer.

Which statement describes the term atomic number for a nucleus?

Which statement describes the term mass number for a nucleus?

Which statement describes the term isotopes ?

of protons

of electrons

of protons

of neutrons

An atom contains 8 protons, 8 neutrons and 8 electrons.

Which of these would result in a negatively charged ion of the same element?

It is not possible to predict exactly when a radioactive nucleus will decay.

Which feature of radioactive decay best explains this observation?

Which of these is the correct unit for measuring the activity of a radioactive sample?

Bismuth‑207 is a gamma emitter and is represented by the symbol

How many neutrons are in the nucleus of an atom of bismuth‑207?

Which of these gives the best description of gamma radiation?

A technician uses this method to investigate the penetration power of gamma radiation.

• place a gamma emitting source at a fixed distance from a radiation detector

• measure the count using the detector, for a period of one minute

• place a thin sheet of lead between the source and the detector

• measure the new count using the detector, for a period of one minute

• increase the number of lead sheets between the source and detector and repeat this process

The table gives some of the variables from the technician’s method.

Complete the table by placing a tick () in each row to show whether each variable is an independent, a dependent or a control variable.

Lead-210 is a radioactive isotope of lead and is represented using this symbol.

State what is meant by the term isotope.

How many protons are in the nucleus of lead-210?

A sample of lead-210 has an initial activity of 240 Bq.

After 66 years, the activity of the sample is 30 Bq.

Calculate the half-life of lead-210.