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Nuclear decay

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Lesson details

Learning outcome

I can use a nuclear equation to represent alpha and beta decays, and describe the particles involved.

Key learning points

  1. A nuclear equation shows the particles in a nuclear decay, including the electric charge and mass number of each one.
  2. An alpha particle consists of two protons and two neutrons, has a mass of 4 and charge of +2.
  3. The protons and neutrons in an alpha particle are held together very strongly.
  4. After an alpha or beta decay, a nucleus usually emits some gamma radiation.
  5. A beta particle is an electron emitted at a high speed from a nucleus, its mass is close to zero and charge of –1.

Keywords

  • Alpha decay - the emission of a particle containing two protons and two neutrons from a nucleus

  • Gamma radiation - the emission of electromagnetic radiation from a nucleus that reduces its energy

  • Beta–minus decay - the conversion of a neutron to a proton with the emission of a high speed electron from a nucleus

  • Nuclear decay equations - show the changes of particles during nuclear decay processes

Common misconception

Pupils may not have a clear understanding of the forces acting between neutrons and protons in an atomic nucleus.

In simple terms, explain the reasons why some nuclei are unstable in terms of electrostatic repulsion, and include ideas about the strong nuclear force attracting protons and neutrons to each other.

Teacher tip

It is not necessary for pupils to recall the reasons for alpha and beta decay, but it is important to explain these reasons so that different types of nuclear decay make logical sense to them.

Licence

This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Prior knowledge starter quiz

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6 Questions

Q1.
A nucleus of a fluorine atom can be represented as $$^{19}_{9}$$F. Match each type of particle to the number of them present in this nucleus.

Correct Answer:protons,9

9

Correct Answer:neutrons,10

10

Correct Answer:nucleons,19

19

Q2.
Which of these statements are correct when comparing two isotopes of the same element.

Correct answer: They must have the same number of protons.
They must have the same number of neutrons.
They must have the same number of nucleons.
They can have different numbers of protons.
Correct answer: They can have different numbers of neutrons.

Q3.
Which of these are isotopes of the same element? (The symbol of each elements is not correct)

Correct answer: $$^{16}_{8}$$E
$$^{18}_{10}$$E
Correct answer: $$^{17}_{8}$$E
$$^{18}_{9}$$E
$$^{16}_{7}$$E

Q4.
Where are the electrons located in the Bohr nuclear model of an atom?

Inside the nucleus bonded to protons.
Orbiting around the nucleus like planets.
Spread throughout a positive sponge.
Correct answer: At specific distances from the nucleus.
Moving freely between atoms.

Q5.
Which force causes protons to repel each other inside the nucleus?

strong nuclear force
gravitational force
Correct answer: electrostatic force
frictional force
magnetic force

Q6.
Which statements help explain why a small nucleus with a similar number of protons and neutrons is more stable than a small nucleus with more protons than neutrons?

The protons produce a repulsive force on neutrons.
Correct answer: The protons produce an attractive force on neutrons.
The protons produce an attractive force on other protons.
Correct answer: The neutrons produce an attractive force on protons and neutrons.
Correct answer: The protons produce a repulsive for on other protons.

Assessment exit quiz

Download exit quiz questions (PDF)

6 Questions

Q1.
Match each keyword or phrase to the correct definition.

Correct Answer:alpha decay,the emission of a particle containing two protons and two neutrons

the emission of a particle containing two protons and two neutrons

Correct Answer:gamma radiation,electromagnetic radiation emitted from a nucleus reducing its energy

electromagnetic radiation emitted from a nucleus reducing its energy

Correct Answer:beta–minus decay,the conversion of a neutron to a proton releasing an electron

the conversion of a neutron to a proton releasing an electron

Correct Answer:nuclear decay equations,show the changes of particles during nuclear decay processes

show the changes of particles during nuclear decay processes

Q2.
Which of these symbols can be used to represent an alpha particle?

Correct answer: $$^{4}_{2}$$He
$$^{2}_{4}$$He
Correct answer: $$^{4}_{2}$$α
$$^{2}_{4}$$α
$$^{4}_{2}$$β

Q3.
Which of these shows the daughter nucleus formed by the alpha decay of thorium-232 ($$^{232}_{90}$$Th)?

$$^{228}_{88}$$Th
$$^{232}_{90}$$Ra
Correct answer: $$^{228}_{88}$$Ra
$$^{230}_{86}$$Rn
$$^{230}_{86}$$Th

Q4.
Which of the following statements about decay by neutron emission are correct?

The charge of the nucleus increases by 1.
The charge of the nucleus decreases by 1.
Correct answer: The charge of the nucleus remains unchanged.
Correct answer: The mass of the nucleus decreases.
The mass of the nucleus remains unchanged.

Q5.
Which of these types of decay is most likely for a light nucleus which has too many neutrons compared to protons?

alpha decay
Correct answer: beta-minus decay
gamma decay
delta decay
neutron emission

Q6.
Which of the following equations correctly shows a beta minus β$$^{-}$$ decay for radium-228 $$^{228}_{88}$$Ra?

Correct answer: $$^{228}_{88}$$Ra -> $$^{228}_{89}$$Ac + $$^{0}_{-1}$$β
$$^{228}_{88}$$Ra -> $$^{228}_{87}$$Fr + $$^{0}_{-1}$$β
$$^{228}_{88}$$Ra -> $$^{229}_{88}$$Ra + $$^{-1}_{0}$$β
$$^{228}_{88}$$Ra -> $$^{228}_{87}$$Fr + $$^{0}_{1}$$β
$$^{228}_{88}$$Ra -> $$^{224}_{86}$$Rn + $$^{4}_{2}$$α

To help you plan your 11 physics lesson on: Nuclear decay, download all teaching resources for free and adapt to suit your pupils' needs...