Radioactivity, Half-Life & Nuclear Decay
Unstable atomic nuclei undergo random radioactive decay by emitting alpha particles, beta particles, or gamma rays to become more stable. This guide covers the plum pudding vs nuclear models of the atom, the penetrating power and ionising ability of alpha, beta, and gamma radiation, nuclear decay equations, and half-life calculations.
- Isotope
- Atoms of the same element that have the same number of protons but a different number of neutrons.
- Alpha Particle
- A particle consisting of two protons and two neutrons (a helium nucleus), with a charge of +2.
- Beta Particle
- A high-speed electron ejected from the nucleus as a neutron turns into a proton.
Radioactivity, Half-Life & Nuclear Decay: Exponential Half-Life Curve & Radiation Shielding
Adjust the number of elapsed half-lives to calculate undecayed nuclei N = N₀ × (½)ⁿ and compare alpha, beta, and gamma absorption.
Key Concepts & Exam Definitions (5)
- Isotope
- Atoms of the same element that have the same number of protons but a different number of neutrons.
- Alpha Particle
- A particle consisting of two protons and two neutrons (a helium nucleus), with a charge of +2.
- Beta Particle
- A high-speed electron ejected from the nucleus as a neutron turns into a proton.
- Gamma Ray
- A high-frequency electromagnetic wave emitted from a nucleus.
- Background Radiation
- The low-level radiation that is around us all the time from natural and man-made sources.
Quick-Fire Flashcards (5)
Click any card to check the answer, then mark it as Known to track your progress.
Which type of radiation is the most ionizing?
What material is needed to stop beta radiation?
What is an alpha particle made of?
How does alpha decay affect the mass number of a nucleus?
What unit is used to measure radioactive activity?
Exam-Style Questions & Mark Schemes (3)
Write or think through your answer first, then click Check Mark Scheme to see the exact points examiners award marks for.
- Q1
A radioactive sample has an initial activity of 800 Bq. If its half-life is 5 days, what will its activity be after 15 days?
Click “Check Mark Scheme” to compare your answer, 15 days is 3 half-lives. 800 -> 400 -> 200 -> 100 Bq.
- Q2
Explain why alpha radiation is highly dangerous if inhaled or swallowed.
Click “Check Mark Scheme” to compare your answer, Alpha particles are highly ionizing, meaning they can cause significant damage to internal cells and DNA, leading to mutations or cancer.
- Q3
Describe what happens to a nucleus during beta decay.
Click “Check Mark Scheme” to compare your answer, A neutron in the nucleus turns into a proton, and a high-speed electron (beta particle) is emitted.
Common Exam Questions (3)
What are the three main types of nuclear radiation?
The three main types of nuclear radiation are alpha particles (α, consisting of 2 protons and 2 neutrons, identical to a helium nucleus), beta particles (β, high-speed electrons ejected from the nucleus when a neutron turns into a proton), and gamma rays (γ, high-frequency electromagnetic waves).
What is a half-life?
The half-life of a radioactive isotope is the average time taken for the number of undecayed radioactive nuclei in a sample (or the count rate/activity) to halve.
What is the difference between contamination and irradiation?
Radioactive contamination is the unwanted presence of radioactive atoms on or inside an object or person, which continues to decay and irradiate tissues. Irradiation is the exposure of an object to nuclear radiation from an external source without the object itself becoming radioactive.
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