Nuclear Physics

What is the collective term for the protons and neutrons that make up an atomic nucleus?

Nucleons.

What does the atomic number, symbolized by Z, represent for an atom's nucleus?

The number of protons.

The total number of protons and neutrons in a nucleus is known as the _.

Mass number (A).

What is the relationship between mass number (A), atomic number (Z), and neutron number (N)?

The mass number is the sum of the atomic and neutron numbers, expressed as $A = Z + N$.

How are nuclear species (nuclides) typically notated, using X for the chemical symbol, A for mass number, and Z for atomic number?

They are notated as $^{A}_{Z}X$.

Atoms of the same element that have the same number of protons but different numbers of neutrons are called what?

Isotopes.

What are nuclides that have the same mass number (A) but different atomic numbers (Z) called?

Isobars.

Nuclides with the same neutron number (N) but different atomic numbers (Z) are known as _.

Isotones.

The radius (R) of a nucleus is empirically related to its mass number (A) by what formula?

$R = R0 A^{1/3}$, where $R0$ is a constant.

What is the approximate value of the constant $R_0$ in the formula for nuclear radius?

The constant $R_0$ is approximately $1.2 \times 10^{-15}$ m or 1.2 fm.

How does the density of a nucleus depend on its mass number (A)?

The density of a nucleus is a constant, independent of the mass number A.

What is the approximate density of nuclear matter?

The density of nuclear matter is approximately $2.3 \times 10^{17}$ kg m$^{-3}$.

How is one atomic mass unit (u) defined?

It is defined as 1/12th of the mass of a neutral carbon-12 atom.

What is the value of 1 atomic mass unit (u) in kilograms?

1 u is approximately $1.660539 \times 10^{-27}$ kg.

What is Einstein's famous mass-energy equivalence relation?

$E = mc^2$, where c is the speed of light in a vacuum.

The energy equivalent of 1 atomic mass unit (u) is approximately how many Mega-electron Volts (MeV)?

1 u is equivalent to approximately 931.5 MeV/c².

What is the 'mass defect' of a nucleus?

It is the difference between the total mass of its individual constituent nucleons and the actual mass of the nucleus.

The energy required to break a nucleus into its constituent protons and neutrons is known as its _.

Nuclear binding energy ($E_b$).

How is the nuclear binding energy ($E_b$) related to the mass defect ($\Delta M$)?

The binding energy is the energy equivalent of the mass defect, given by $E_b = \Delta M c^2$.

What is the 'binding energy per nucleon' ($E_{bn}$), and what does it indicate?

It is the total binding energy divided by the mass number ($E_b/A$) and indicates the average energy required to remove one nucleon, signifying nuclear stability.

In the plot of binding energy per nucleon versus mass number, which region corresponds to the most stable nuclei?

The flat middle region, for mass numbers between 30 and 170, where the binding energy per nucleon is nearly constant at about 8 MeV.

The binding energy per nucleon curve reaches a maximum of about 8.75 MeV for nuclei with a mass number (A) around _.

56 (e.g., Iron-56).

How does the binding energy per nucleon of very light nuclei (A ≤ 10) compare to that of heavier nuclei?

The binding energy per nucleon is significantly lower for very light nuclei.

The force that binds nucleons together, overcoming the electrostatic repulsion between protons, is called the _.

Nuclear force (or strong nuclear force).

What is a key characteristic of the nuclear force concerning its range?

It is a very short-range force, effective only over distances of a few femtometres.

How does the nuclear force compare in strength to the Coulomb and gravitational forces?

It is much stronger than the Coulomb force and vastly stronger than the gravitational force.

What does it mean that the nuclear force is 'charge-independent'?

The force is approximately the same between proton-proton, neutron-neutron, and proton-neutron pairs.

At what separation distance does the nuclear force between two nucleons change from attractive to strongly repulsive?

The force becomes strongly repulsive at distances less than about 0.8 fm.

The constancy of binding energy per nucleon for medium and heavy nuclei is a consequence of which property of the nuclear force?

The short-range nature of the nuclear force, also referred to as its saturation property.

What is radioactivity?

It is the spontaneous nuclear phenomenon in which an unstable nucleus undergoes decay by emitting particles or radiation.

What particle is emitted during alpha ($\alpha$) decay?

A helium nucleus ($^4_2$He).

What particles are emitted during beta ($\beta$) decay?

Electrons or positrons.

What is emitted during gamma ($\gamma$) decay?

High-energy photons (electromagnetic radiation).

How is energy released in nuclear processes related to the binding energy of the nuclei involved?

Energy is released when nuclei with less total binding energy transform into nuclei with greater total binding energy.

The process where a heavy nucleus, such as uranium, splits into two or more intermediate-mass fragments is called _.

Nuclear fission.

According to the binding energy curve, why does the fission of a heavy nucleus (A=240) into two smaller nuclei (A=120) release energy?

Because the binding energy per nucleon is higher for the fragment nuclei (e.g., ~8.5 MeV) than for the original heavy nucleus (~7.6 MeV).

What is the approximate amount of energy released per fission event of a $^{235}$U nucleus?

The energy released is on the order of 200 MeV.

The process where two light nuclei combine to form a heavier nucleus is known as _.

Nuclear fusion.

Why does nuclear fusion require extremely high temperatures and pressures?

To give the positively charged nuclei enough kinetic energy to overcome their mutual Coulomb repulsion barrier.

Fusion that is achieved by raising the temperature of a system to extremely high levels is called _ fusion.

Thermonuclear fusion.

What is the primary source of energy generation in the sun and other stars?

Thermonuclear fusion of hydrogen into helium.

What is the name of the multi-step fusion process that powers the Sun?

The proton-proton (p, p) cycle.

What is the net result of the proton-proton cycle in the sun?

Four hydrogen atoms (protons) combine to form one helium-4 atom, releasing about 26.7 MeV of energy.

In a nuclear reaction, are the numbers of protons and neutrons conserved separately?

Yes, the total number of protons and the total number of neutrons are separately conserved on both sides of the reaction.

How is mass converted into energy in a nuclear reaction, if the number of nucleons is conserved?

The difference in the total binding energy of the nuclei on each side of the reaction appears as released or absorbed energy, which corresponds to a change in total mass.

The lightest isotope of hydrogen, whose nucleus consists of a single proton, is called a _.

Protium (the nucleus itself is a proton).

What are the names of the two heavier isotopes of hydrogen?

Deuterium and tritium.

What is the composition of a deuterium nucleus ($^2_1$H)?

One proton and one neutron.

What is the composition of a tritium nucleus ($^3_1$H)?

One proton and two neutrons.

Who discovered the neutron in 1932?

James Chadwick.

Is a free neutron stable?

No, a free neutron is unstable and decays into a proton, an electron, and an antineutrino with a mean life of about 1000s.

Compare the energy released from the fission of 1 kg of uranium to the energy from burning 1 kg of coal.

The fission of 1 kg of uranium generates about a million times more energy ($10^{14}$ J) than burning 1 kg of coal ($10^7$ J).

What is the purpose of a moderator (e.g., heavy water, graphite) in a nuclear reactor?

To slow down the fast-moving neutrons produced during fission, making them more likely to cause further fission events.

What is the function of control rods (e.g., cadmium, boron) in a nuclear reactor?

To absorb neutrons and thus control the rate of the fission chain reaction.

An uncontrolled nuclear chain reaction is the principle behind what device?

An atom bomb (nuclear bomb).

A hydrogen bomb is based on which nuclear process?

Nuclear fusion.