IGCSE Physics (0625) 5.1.1 The atom Paper 4-2023,2024&2025

Question

Fig. 10.1 represents a neutral atom of an isotope of element X.
image
(a) State one similarity between this atom and a neutral atom of a different isotope of element X.

(b)    The isotope of element X is radioactive. It decays to form an isotope of element Y by emitting a β-particle.
(i)Using Fig. 10.1 deduce the nuclide notation for the isotope of Y produced by this decay.
nuclide notation:(ii) β-particles ionise the air they pass through less strongly than the same number of α-particles.
Suggest why this is so.

Answer/Explanation

Answer:

(a) equal number of electrons OR equal number of protons

(b) (i) \(^{13}_5\)X
\(^0_{-1}\)β
\(^{13}_6\)Y

(b) (ii) any three from:
• β-particles have charge of smaller size
• β-particles have smaller mass
• β-particles have less energy
• β-particles travel faster / less time near to air molecule
• effect / force on electrons in air molecules less

Question

(a) The isotope hydrogen-1 has a proton number of 1 and a nucleon number of 1.
Two isotopes of helium are helium-3 and helium-4.
Helium-3 has a proton number of 2 and a nucleon number of 3.
Helium-4 has a nucleon number of 4.
Complete Table 11.1 for neutral atoms of these isotopes of helium.

                                                                      Table 11.1

 

helium-3

helium-4

number of neutrons

   

number of electrons

   

mass compared to a neutral atom of hydrogen-1

   

(b) An experiment takes place in a laboratory shielded from all background radiation. A sample of radioactive material is wrapped in aluminium foil of thickness 0.1 mm. A detector of ionising radiation placed 1 cm from the foil records a reading.

A piece of aluminium of thickness 5 mm is placed between the detector and the foil. The detector reading drops to zero.
State and explain any type of radiation passing through the aluminium foil.

Answer/Explanation

Answer:

(a) neutrons 1 2
electrons 2 2
mass 3 4 OR 2 more 3 more

(b) β
β – (would be) stopped by 5 mm / thick Al
α – (would be) stopped by 0.1 mm Al / Al foil
AND γ – (would) not (be) stopped by 5 mm / thick Al

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