GCSE Physics revision

Radioactive decay and nuclear radiation

Atoms and nuclear radiation

AQA 4.4.2.1

Your specification

AQA student objectives

Learning pathway

ALL 🎯

Apply their knowledge to the uses of radiation and evaluate the best sources of radiation to use in a given situation.

MOST 🎯🎯

Interpret results or representations related to radioactive decay and nuclear radiation.

SOME 🎯🎯🎯

Analyse an unfamiliar problem involving radioactive decay and nuclear radiation and justify the method or conclusion.

Revision summary

Read on screen, then print for Cornell-style active revision.

An alpha particle consists of two protons and two neutrons, identical to a helium nucleus, and is represented as 42 He.
Alpha particles can also be written using the Greek letter α, but both notations are acceptable in GCSE nuclear equations.

During alpha decay, an unstable nucleus emits an alpha particle, losing 2 from its atomic number and 4 from its mass number.
For example, uranium-238 (238 ) undergoes alpha decay to form thorium-234 (234
{90}\text{Th}) plus an alpha particle.
When radium-226 (226 ) undergoes alpha decay, it produces radon-222 (222
{86}\text{Rn}) plus an alpha particle.
You must always check the periodic table to identify the new element formed, since the atomic number has changed.
Both the mass numbers and atomic numbers must balance on each side of the nuclear equation.

2. Alpha Decay EquationsAQA

During alpha decay, an unstable nucleus emits an alpha particle, losing 2 from its atomic number and 4 from its mass number.
For example, uranium-238 (238 ) undergoes alpha decay to form thorium-234 (234
{90}\text{Th}) plus an alpha particle.
When radium-226 (226 ) undergoes alpha decay, it produces radon-222 (222
{86}\text{Rn}) plus an alpha particle.
You must always check the periodic table to identify the new element formed, since the atomic number has changed.
Both the mass numbers and atomic numbers must balance on each side of the nuclear equation.

In beta decay, a neutron in the nucleus turns into a proton and emits a fast-moving electron called a beta particle (0−1 e).
Because a neutron becomes a proton, the atomic number increases by 1, but the mass number stays the same.
For example, carbon-14 (14 ) undergoes beta decay to form nitrogen-14 (14 {7}\text{N}) plus a beta particle.
The beta particle is written with a 0 on top (negligible mass) and −1 on the bottom (charge of −1), whether shown as 0−1 e or the Greek letter β.

3. Beta Decay EquationsAQA

In beta decay, a neutron in the nucleus turns into a proton and emits a fast-moving electron called a beta particle (0−1 e).
Because a neutron becomes a proton, the atomic number increases by 1, but the mass number stays the same.
For example, carbon-14 (14 ) undergoes beta decay to form nitrogen-14 (14 {7}\text{N}) plus a beta particle.
The beta particle is written with a 0 on top (negligible mass) and −1 on the bottom (charge of −1), whether shown as 0−1 e or the Greek letter β.

Gamma radiation is pure electromagnetic energy with no mass and no charge, so it is represented by the Greek letter γ.
Because gamma rays carry no mass or charge, emitting a gamma ray does not change the atomic number or mass number of the nucleus.
For example, thorium-234 undergoing gamma decay simply produces thorium-234 again plus a gamma ray: 234 .

4. Gamma Radiation EquationsAQA

Gamma radiation is pure electromagnetic energy with no mass and no charge, so it is represented by the Greek letter γ.
Because gamma rays carry no mass or charge, emitting a gamma ray does not change the atomic number or mass number of the nucleus.
For example, thorium-234 undergoing gamma decay simply produces thorium-234 again plus a gamma ray: 234 .

In neutron emission, a nucleus releases a neutron, so only the mass number decreases by 1 while the atomic number stays the same.
For example, beryllium-9 decays into beryllium-8 plus a neutron: 9 .

In any nuclear equation, the total mass numbers (top numbers) on the left must equal the total mass numbers on the right.
Similarly, the total atomic numbers (bottom numbers) must also balance on both sides of the equation.
Always use the periodic table to identify any unknown element produced after a decay, using its new atomic number.

6. Balancing Nuclear EquationsAQA

In any nuclear equation, the total mass numbers (top numbers) on the left must equal the total mass numbers on the right.
Similarly, the total atomic numbers (bottom numbers) must also balance on both sides of the equation.
Always use the periodic table to identify any unknown element produced after a decay, using its new atomic number.