CAIE A-Level Physics AS 11.1 Atoms Nuclei and Radiation Questions

Practise using scattering evidence, nuclear notation, isotopes and conservation laws to explain the nucleus and alpha, beta and gamma decay.

Exam points

infer nuclear size, charge and mass concentration from alpha-scattering results and describe the nuclear atom
use nucleon/proton numbers, isotopes and A Z X notation to determine nuclear composition and charge
apply conservation of charge and nucleon number to alpha- and beta-decay equations
describe alpha, beta-minus, beta-plus and gamma radiation, including antiparticles, neutrinos and energy spectra
use the unified atomic mass unit u in nuclear and particle contexts

Covered syllabus points

11.1.1—The results of the α-particle scattering experiment the existence and small 11.1.2—A simple model for the nuclear atom to include protons, neutrons and orbital 11.1.3—Nucleon number and proton number 11.1.4—Isotopes are forms of the same element with different numbers of neutrons in 11.1.5—The notation A Z X for the representation of nuclides 11.1.6—Nucleon number and charge are conserved in nuclear processes 11.1.7—The composition, mass and charge of α-, β- and γ-radiations (both β–11.1.8—An antiparticle has the same mass but opposite charge to the corresponding 11.1.9—That (electron) antineutrinos are produced during β– decay and (electron)11.1.10—Α-particles have discrete energies but that β-particles have a continuous 11.1.11—Α- and β-decay by a radioactive decay equation of the form UT h92 238 90 234 11.1.12—The unified atomic mass unit (u) as a unit of mass

[Maximum number: 1]

Which statement about the alpha-particle scattering experiment provides evidence for the existence of the nucleus?

A tiny proportion of the alpha-particles are deflected through large angles.

Slower alpha-particles are deflected through larger angles.

The kinetic energies of the deflected alpha-particles are unchanged.

The number of alpha-particles deflected depends on the thickness of the foil.

[Maximum number: 7]

(a)

Describe the structure of an atom of uranium-238, $\stackrel{238}{92} \mathrm{U}$ .

[ 2 ]

(b)

The decay of uranium-238 is shown by the equation

{ }_{92}^{238} \mathrm{U} \rightarrow{ }_{90}^{234} \mathrm{Th}+\mathrm{X} .

For nucleus X , calculate the ratio, in $\mathrm{Ckg}^{-1}$ , of $\frac{\text { charge }}{\text { mass }}$ .
ratio = $\mathrm{C} \mathrm{kg}^{-1}$

[ 3 ]

charge =2 e
$\left(=2 \times 1.60 \times 10^{-19} \mathrm{C}\right)$
mass =4 u
$\left(=4 \times 1.66 \times 10^{-27} \mathrm{~kg}\right)$
ratio $=\left(2 \times 1.60 \times 10^{-19}\right) /\left(4 \times 1.66 \times 10^{-27}\right)$ $=4.8 \times 10^{7} \mathrm{C} \mathrm{~kg}^{-1}$

(c)

Two particles P and Q each consist of three quarks. These quarks are up (u) or down (d) quarks.

Particle P has no overall charge.
Particle Q has an overall charge of +2 e, where e is the elementary charge.
State the quark composition of:

[ 2 ]

(i)

particle P

[ 1 ]

(ii)

particle Q.

[ 1 ]

[Maximum number: 1]

The table lists the nucleon number and the proton number of various nuclei. The nuclei are represented by the letters L to T.

Table for Question 3 — CAIE A-Level Physics AS

Which row in the following table correctly shows three nuclei of the same element, and three nuclei that have the same number of neutrons?

same element

same number

of neutrons

LM N

RPN

MPS

RST

OPQ

MPS

RPN

OPQ

[Maximum number: 2]

Describe the structure of an atom of uranium-238, $\stackrel{238}{92} \mathrm{U}$ .

[Maximum number: 1]

Hydrogen and deuterium can be represented by the nuclide symbols ${ }_{1}^{1} \mathrm{H}$ and ${ }_{1}^{2} \mathrm{H}$ respectively.
What is a difference between hydrogen and deuterium?

The deuterium atom has twice the number of electrons as the hydrogen atom.

The deuterium nucleus has a charge, but the hydrogen nucleus has no charge.

The deuterium nucleus has less mass than the hydrogen nucleus.

The deuterium nucleus has half the charge per unit mass of the hydrogen nucleus.

[Maximum number: 1]

Radon-211, ${ }_{86}^{211} \mathrm{Rn}$ , francium-210, ${ }_{87}^{210} \mathrm{Fr}$ , and radium-212, $\underset{88}{212} \mathrm{Ra}$ , are three nuclides.
How many neutrons does each nuclide have in its nucleus?

radon-211

francium-210

radium-212

125

123

124

211

210

212

297

300

[Maximum number: 1]

An unstable nucleus of an element decays by emitting an $\alpha$ -particle or a $\beta^{-}$ particle to become a nucleus of a different element. This nucleus is also unstable and emits an $\alpha$ -particle or a $\beta^{-}$ particle. The process continues until an isotope of the original element is produced.

What is the minimum possible number of these particles emitted?

[Maximum number: 1]

The charge-to-mass ratio r of a particle is given by the equation shown.

r=\frac{\text { charge on particle }}{\text { mass of particle }}

The value of r is determined for an $\alpha$ -particle, a $\beta^{+}$ particle and a proton p .
Which list shows the particles in order of increasing magnitude of r from left to right?

$\alpha \rightarrow \beta^{+} \rightarrow p$

$\alpha \rightarrow p \rightarrow \beta^{+}$

$\mathrm{p} \rightarrow \alpha \rightarrow \beta^{+}$

$p \rightarrow \beta^{+} \rightarrow \alpha$

[Maximum number: 1]

A proton has mass $m_{p}$ and charge +e.
What are the mass and charge of an antiproton?

mass

charge

$-m_{\mathrm{p}}$

-e

$m_{\mathrm{p}}$

-e

[Maximum number: 1]

Nuclide X with proton number Z undergoes $\beta^{+}$ decay to form nuclide Y .
The decay may be represented by the equation shown.

X \rightarrow Y+\beta^{+}+W

What is the proton number of Y and which particle is represented by the symbol W ?

proton number

of Y

particle

represented by W

$\mathrm{Z}-1$

antineutrino

$\mathrm{Z}-1$

neutrino

$\mathrm{Z}+1$

antineutrino

$\mathrm{Z}+1$

neutrino

[Maximum number: 1]

Which statement about radioactive decay is correct?

Neutrinos are always emitted during $\alpha$ -decay.

The $\alpha$ -particles emitted from a radioactive sample have a continuous range of kinetic energies.

The $\beta^{-}$ particles emitted from a radioactive sample have a continuous range of kinetic energies.

The proton number of a nucleus decreases by four when it undergoes $\alpha$ -decay.

[Maximum number: 1]

Nucleus P has 144 neutrons and 93 protons. Nucleus P is unstable and undergoes $\alpha$ -decay to form nucleus Q. Nucleus Q then undergoes $\beta^{-}$ decay to form nucleus R.

Nucleus P is represented by point P on the graph.
Which point on the graph represents nucleus R?

Figure for Question 12 — CAIE A-Level Physics AS

[Maximum number: 1]

The discovery of a particle with an unusual charge was an important step in the development of the theory of quarks. The particle is a hadron with a mass of $2.19 \times 10^{-27} \mathrm{~kg}$ and a charge of +2 e, where e is the elementary charge.

Calculate the mass, in u, of the particle. Give your answer to three significant figures.
mass = u

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Covered syllabus points

Question 1

Question 2

Question (a)

Question (b)

Question (c)

Question (i)

Question (ii)

Question 3

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Question 13