Nuclear and Particle Physics Review

Comprehensive practice flashcards covering atomic structure, radioactive decay processes, particle physics, and quark theory based on the lecture notes.

How does the alpha-scattering experiment give evidence of a small and dense nucleus?

A few alpha particles bounce back, suggesting they hit a dense positive charge rather than an evenly distributed charge (like the Plum Pudding Model). The small number of occurrences indicates that the nucleus must be small.

How are atomic particles arranged within an atom?

Protons and Neutrons reside within the nucleus, while Electrons orbit the nucleus in surrounding shells.

Which has higher density: an atom or a nucleus?

A nucleus is much more dense than an atom since the atom includes a lot of empty space.

What is the unified atomic mass unit ($u$)?

The unified atomic mass unit ($u$) is defined as $\frac{1}{12}$ of the mass of a Carbon-12 atom and is approximately equal to the average mass of a nucleon.

What is the definition of an isotope?

Isotopes are atoms of an element (with the same number of protons) with a different number of neutrons, which results in a different mass number.

What is an ion?

Ions are similar to atoms but are charged because they contain an unequal number of protons and electrons.

What is an alpha ($\alpha$) particle?

An alpha particle is a fast moving Helium $2+$ ion consisting of a nucleus containing $2$ protons and $2$ neutrons.

What is the mass and relative charge of beta ($\beta$) particles?

Both $\beta^-$ and $\beta^+$ particles have a negligible mass of $9.11 \times 10^{-31}\,kg$. $\beta^-$ particles have a relative charge of $-1$ ($-1.6 \times 10^{-19}\,C$) and $\beta^+$ particles have a relative charge of $+1$ ($+1.6 \times 10^{-19}\,C$).

What are gamma ($\gamma$) rays?

Gamma rays are short wavelength, high energy electromagnetic radiation often emitted during radioactive decay, having zero mass and zero charge.

What is the decay equation for Uranium-238 undergoing alpha ($\alpha$) decay?

$$^{238}U \rightarrow ^{234}Th^{2-} + ^{4}\alpha^{2+}$$

What is the decay equation for Carbon-14 undergoing $\beta^-$ decay?

$^{14}C \rightarrow ^{14}N^{+} + e^{-} + \bar{\nu}$, where $\bar{\nu}$ is an anti-neutrino.

What is the decay equation for Carbon-10 undergoing $\beta^+$ decay?

$^{10}C \rightarrow ^{10}N^{-} + e^{+} + \nu$, where $e^{+}$ is a positron and $\nu$ is a neutrino.

Which type of radiation can only be stopped by a thick block of lead or concrete?

Gamma radiation

In terms of $A$ and $Z$, what are the nucleon and atomic numbers of a particle after alpha decay?

Nucleon number = $A - 4$; Atomic number = $Z - 2$

How does the atomic number change in beta plus decay?

It decreases because a proton turns into a neutron and a positron.

Why does beta plus decay have a very low penetration?

The positrons will be annihilated by electrons almost immediately.

Give a difference and a similarity between particles and their antiparticles.

Similarity: They have a similar mass. Difference: They have opposite charges.

Why do beta decay particles possess a continuous range of energies whereas alpha particles possess distinct energies?

In beta decay, energy is shared between the electron/positron and the neutrino/anti-neutrino, allowing a continuous range. In alpha decay, only the alpha particle is emitted at distinct energies.

What are quarks?

Quarks are fundamental elementary constituents of matter: the basic unit from which all nuclear sub-atomic particles are constructed.

What are the six types of quark?

Up (u), Down (d), Strange (s), Charm (c), Top (t), and Bottom (b).

State the quark compositions of protons and neutrons.

Protons: two up quarks ($+2/3e$) and a down quark ($-1/3e$). Neutrons: one up quark ($+2/3e$) and two down quarks ($-1/3e$).

What is a hadron?

A hadron is a sub-atomic particle comprising two or more quarks held together by the strong nuclear force.

What are leptons?

Leptons are fundamental particles which are not subject to the strong nuclear force, though they interact via the weak nuclear force.

State the charges of the up, down, and strange quarks in terms of electron charge $e$.

Up = $+2/3e$; Down = $-1/3e$; Strange = $-1/3e$.

What is meant by beta minus decay?

A neutron turns into a proton and the atom releases an electron and an anti electron neutrino.

Which quark transition occurs in beta minus decay?

A down quark turns into an up quark (emitting an anti-neutrino).

Which quark transition occurs in beta plus decay?

An up quark is converted to a down quark (emitting a neutrino).

What quantities must be conserved during the decay of particles?

Charge, mass, baryon number, lepton number, and energy.

What are the defining features of radioactive decay?

Radioactive decay is spontaneous and random, making it impossible to predict when an individual nucleus will decay.

What features of a nucleus might cause it to radioactively decay?

Too many or too few neutrons; being too heavy (too many nucleons); or having too much energy.