Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 5.1.2 — The nucleus (Part a)
• Topic 5.2.2 — The three types of nuclear emission (Part b)
• Topic 5.2.5 — Safety precautions (Part c)
(a)
An atom consists of a central nucleus containing positively charged protons and neutral (zero charge) neutrons. Therefore, the nucleus contains the majority of the atom’s mass and has an overall positive charge. Negatively charged electrons are much smaller particles that orbit outside the nucleus in specific energy levels or shells.
(b)
Type P is $\beta$ / beta (particle)
Type Q is $\alpha$ / alpha (particle)
Type R is $\gamma$ / gamma (ray)
Alpha ($\alpha$) particles have the lowest penetrating power because they are relatively large and highly ionizing; they are easily stopped by a thin sheet of paper, identifying Q as alpha. Beta ($\beta$) particles are smaller and faster, making them more penetrating than alpha; they pass through paper but are stopped by a few millimeters of aluminium, identifying P as beta. Gamma ($\gamma$) rays are high-energy electromagnetic waves with the highest penetrating power, passing through both paper and aluminium, identifying R as gamma.
(c)
Any two from:
• use a lead (lined) box / container or concrete room
• idea of remote / area location / away from main building
• locked room / secure area
• radiation sign on door / in place
• only remove / use for short time
Radioactive materials emit ionizing radiation that can cause cell damage, mutations, or cancer in living tissues. To minimize exposure risks, they must be shielded using dense materials like lead or thick concrete which absorb the radiation. Additionally, storing them in secure, locked rooms with clear warning hazard signs prevents unauthorized access, and maintaining distance reduces the intensity of any exposure.
