11 Particle physicsAS Level

11.1 Atoms, nuclei and radiation

12 of 12 objectives have lessons · 0 studied · 0 secure

Lessons

How alpha particles revealed the nucleusMost alpha particles sail through a gold foil, a few bend, and a tiny fraction bounce back — which tells us the atom is mostly empty with a small, positive, heavy nucleus. 7 min, not started
The simple nuclear model of the atomA tiny nucleus of protons and neutrons surrounded by orbiting electrons, with the atom itself almost entirely empty space. 6 min, not started
Nucleon number and proton numberProton number counts the protons, nucleon number counts protons plus neutrons, and the difference gives the neutrons. 7 min, not started
IsotopesIsotopes of an element have the same number of protons but different numbers of neutrons, so their chemical behaviour matches but their masses differ. 7 min, not started
Nuclide notationWriting the nucleon number as a superscript and the proton number as a subscript in front of the element symbol records everything a nucleus contains. 6 min, not started
Conservation of charge and nucleon numberIn every nuclear change the total charge and the total number of nucleons are the same before and after, which is what makes decay equations balance. 8 min, not started
Alpha, beta and gamma radiationThe three radiations differ in what they consist of, so they carry different masses and charges — alpha +2e and 4 u, beta ∓e, gamma neither. 9 min, not started
Antiparticles and the positronAn antiparticle has the same mass as its particle but the opposite charge, so the positron is the electron's antiparticle. 6 min, not started
Neutrinos and antineutrinosBeta-minus decay emits an electron antineutrino and beta-plus decay emits an electron neutrino, particles with no charge and almost no mass. 7 min, not started
Alpha and beta energy spectraAlpha particles leave with a few definite energies, while beta particles show a continuous spread because the energy is shared with a neutrino. 8 min, not started
Writing alpha and beta decay equationsEvery alpha or beta decay can be written as a balanced equation in nuclide notation, with A falling by 4 or staying the same and Z changing by 2, 1 or −1. 9 min, not started
The unified atomic mass unitThe unified atomic mass unit u is defined from carbon-12 and equals 1.66 × 10⁻²⁷ kg, which makes nuclear masses easy to write and to compare. 7 min, not started

Syllabus objectives

12 objectives

What Cambridge says you should be able to do, in our words. Codes are the topic number plus the objective’s position.

11.1.1

Infer from the results of the α-particle scattering experiment that the nucleus exists and is small.

Taught in: How alpha particles revealed the nucleus · 5 questions

11.1.2

Describe a simple nuclear model of the atom made up of protons, neutrons and orbital electrons.

Taught in: The simple nuclear model of the atom · 5 questions

11.1.3

Distinguish between nucleon number and proton number.

Taught in: Nucleon number and proton number · 6 questions

11.1.4

Understand that isotopes are forms of one element whose nuclei contain different numbers of neutrons.

Taught in: Isotopes · 6 questions

11.1.5

Understand and use the nuclide notation A over Z X (nucleon number A as a superscript and proton number Z as a subscript, written before the element symbol X) to represent nuclides.

Taught in: Nuclide notation · 6 questions

11.1.6

Understand that charge and nucleon number are both conserved in nuclear processes.

Taught in: Conservation of charge and nucleon number · 6 questions

11.1.7

Describe the composition of α-, β- and γ-radiations, together with their mass and charge.

Includes both β⁻ (electrons) and β⁺ (positrons).

Taught in: Alpha, beta and gamma radiation · 6 questions

11.1.8

Understand that an antiparticle has the same mass as its corresponding particle but the opposite charge, and that the positron is the electron’s antiparticle.

Taught in: Antiparticles and the positron · 5 questions

11.1.9

State that β⁻ decay produces (electron) antineutrinos and β⁺ decay produces (electron) neutrinos.

Taught in: Neutrinos and antineutrinos · 5 questions

11.1.10

Understand that α-particles are emitted with discrete energies, while β-particles have a continuous range of energies because (anti)neutrinos are also emitted in β-decay.

Taught in: Alpha and beta energy spectra · 5 questions

11.1.11

Represent α- and β-decay with radioactive decay equations of the form ²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂α.

Taught in: Writing alpha and beta decay equations · 6 questions

11.1.12

Use the unified atomic mass unit (u) as a unit of mass.

Taught in: The unified atomic mass unit · 6 questions