Nuclear (M6)

Question 1

Proton number

Answer 1

The atomic number - the number of protons in an element’s nucleus.
Symbol: Z

Question 2

Nucleon number

Answer 2

The mass number - the total number of protons and neutrons in a nucleus.
Symbol: A

Question 3

Isotope

Answer 3

Nuclei of the same element that have the same atomic number (Z) but different nucleon numbers (A).
Different numbers of neutrons.

Question 4

Hadron

Answer 4

A particle or antiparticle that is affected by the strong nuclear force and, if charged, the electromagnetic force.
Eg proton (uud), neutron (udd)

Question 5

Baryon

Answer 5

Any hadron made with a combination of three quarks eg a proton.

Question 6

Meson

Answer 6

Any hadron made with a combination of a quark and an anti-quark eg kaon and pion

Question 7

Fundamental particle

Answer 7

A particle that has no internal structure and hence cannot be split into smaller particles.

Question 8

Lepton

Answer 8

A fundamental particle or antiparticle that is not affected by the strong nuclear force.
Eg electron or positron

Question 9

Ionising radiation

Answer 9

Any form of radiation that can ionise an atom by removing an electron to leave a positive ion.

Question 10

Random decay

Answer 10

Cannot predict when or which nucleus will decay. Each nucleus has the same chance of decaying per unit time.

Question 11

Spontaneous decay

Answer 11

Unaffected by the presence of other nuclei or external factors such as pressure or temperature.

Question 12

Annihilation

Answer 12

The complete destruction of a particle and its antiparticle in an interaction that releases energy in the form of identical photons.

Question 13

Rest mass

Answer 13

The mass of an object such as a particle when it is stationary

Question 14

Mass defect

Answer 14

The difference between the mass of a nucleus and the mass of its completely separated constituent nucleons.

Question 15

Binding energy

Answer 15

The minimum energy required to completely separate a nucleus into its constituent protons and neutrons.

Question 16

Binding energy per nucleon

Answer 16

The binding energy divided by the number of nucleons. The greater the binding energy per nucleon, the more tightly bound the nucleons in the nucleus, therefore the more stable the atom.

Question 17

Binding energy curve

Answer 17

Increases rapidly, Iron 56 at peak then decreases slowly.
Fusion on left
Fission on right

Question 18

Induced fission

Answer 18

Nuclear fission occurring when a nucleus becomes unstable on absorbing another particle

U-235 + n = U-236 = Ba-141 + Kr-92 + 3n

Question 19

Fusion

Answer 19

A process in which two smaller nuclei join together to form one larger nucleus.

Question 20

Chain reaction

Answer 20

A reaction in which the neutrons from an earlier fission stage are responsible for further fission reactions leading to an exponential growth in the rate of the reactions.

Question 21

Components of a fission reactor

Answer 21

Fuel rods: contain enriched uranium (2-3% U-235, the rest U-238)

Moderator: slows the fast neutrons - normally water which is also used as a coolant

Control rods: material absorbs neutrons so exactly one survives per reaction

Question 22

Carbon dating

Answer 22

A method for determining the Age of organic material by comparing the activities or ratios of carbon-14 nuclei of the dead material of interest and similar living material.

Question 23

Exponential decay equation

Answer 23

N = N⁰ e^-lt

l = decay constant

When t = its half life: N = N⁰/2

Question 24

Half life

Answer 24

The average time it takes for half the number of active nuclei in a sample of an isotope to decay.

Question 25

Activity

Answer 25

The rate at which nuclei decay or disintegrate in a radioactive source.
Unit: Becquerels (Bq)

Question 26

Decay constant

Answer 26

The probability of decay of an individual nucleus per unit time.

Question 27

Strong nuclear force

Answer 27

One of the four fundamental forces in nature, acting on hadrons and holding nuclei together.
Very short range - repulsive below 0.5fm and attractive up to about 3fm
Force carrier: gluon

Question 28

Weak nuclear force

Answer 28

One of the four fundamental forces.
Responsible for beta decay.
Range of about 10^-18m and 10^-6 X strength of SNF
Force carrier: boson

Question 29

Alpha radiation properties

Answer 29

Charge: 2e
Range: a few cm
Absorption: thin sheet of paper
Typical speed: 10^6 ms
Mass: 4.00151u
Equation: (A, Z)X -> (A-4, Z-2)Y + (4,2)He

Question 30

Beta radiation properties

Answer 30

Charge: e or -e
Range: 1m
Absorption: 1-3mm of aluminium
Typical speed: 10^8 ms
Mass: 0.00055u
Plus equation: (A,Z)X -> (A,Z-1)Y + (0,1)e + Ve
Minus equation: (A,Z)X -> (A,Z+1)Y + (0,-1)e + Vē

Question 31

Gamma radiation properties

Answer 31

Charge: 0
Absorption: a few cm of lead
Typical speed: 3x10^8 ms
Mass: 0
Equation: X -> X + g

Question 32

Measuring half-life of protactinium

Answer 32

Plastic bottle with solution of uranyl nitrate in water and organic solvent containing protactinium.
First measure background count rate
Shake bottle so protactinium dissolves in organic solvent which floats to the top.
Place GM tube pointing at organic layer (not touching bottle) and measure count rate for 10s every 30s.
Calculate CCR
Plot graph of CCR against time.