A-LevelPhysicsNuclear physics9702/22 · Feb/Mar 2021 · Q76 Marks

The results of the α-particle scattering experiment provide evidence for the structure of the atom. Result 1: The vast majority of the α-particles pass straight through the metal foil or are deviated by small angles. Result 2: A very small minority of α-particles is scattered through angles greater than 90°. State what may be inferred (deduced) from:

(a)(i)result 1[1]
(a)(ii)result 2.[2]
(b)(i)A radioactive decay sequence contains four nuclei, P, Q, R and S, as shown. ²¹⁸₈₄P → ²¹⁴₈₂Q → ²¹⁴₈₃R → S Nucleus S is an isotope of nucleus P. (i) Determine the proton number and the nucleon number of nucleus S. proton number = ..................................................... nucleon number = .....................................................[2]
(b)(ii)The quark composition of a nucleon in Q changes as Q decays to form R. Describe this change to the quark composition of the nucleon.[1]

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2021). The mark or mark type is shown in brackets.

[B1] (a)(i) most of the atom is empty space or the nucleus (volume) is very small compared to the atom
[B1] (a)(ii) the nucleus is charged
[B1] (a)(ii) the mass is concentrated in nucleus / small region / small volume / small core or the majority of the mass is in nucleus / small region / small volume / small core
[A1] (b)(i) proton number = 84
[A1] (b)(i) nucleon number = 214
[B1] (b)(ii) up down down changes to up up down / udd → uud or down changes to up / d → u

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