Nuclear Physics

Isotopes (Definition)

Atoms of the same element which have different numbers of neutron

What element has the lowest number of isotopes?

Hydrogen

What are the three atoms/isotopes of hydrogen?

Hydrogen. Deuterium. Tritium

Proton and neutron counts of hydrogen

1 proton and 0 neutrons

Proton and neutron counts of deuterium

1 proton and 1 neutrons

Proton and neutron counts of tritium

1 proton and 2 neutrons

Draw a diagram of hydrogen

Draw a diagram of deuterium

Draw a diagram of tritium

Which hyrdogen isotope is radioactive?

Tritium

How are isotopes identical?

Chemically identical to one another

Mass defect (Definition)

The difference between the mass of the atom and the sum of the masses of its constituent parts

Binding energy (Definition)

The amount of energy that must be supplied to a nucleus to completely separate its nuclear particles. Binding energy is the energy equivalent of the mass defect

Binding energy per nucleon (Definition)

Binding energy divided by the number of nucleons (protons + neutrons)

Explain binding energy

When an atom other than Hydrogen is made a little bit of mass disappears. This missing mass is converted to binding energy to keep positively charged protons together in the nucleus

What formula is linked to binding energy?

E = mc²

Why do larger atoms have more binding energy?

Binding energy has to be spread over more nucleons

How to find how well stuck together different nuclei are?

Work out binding energy and divide it by the number of nucleons in the nucleus

Draw a graph of binding energy for a nucleon versus mass number

What is the most stable isotope?

Fe - 56

How do light nuclei become more stable?

Become more heavier via nuclear fusion

Examples of light nuclei

Hydrogen. Helium

How do heavy nuclei become more stable?

Become lighter by spitting out abit of themselves (radiation) or fission

Examples of heavy nuclei

Uranium. Plutonium

Does fusion or fission release more energy? Why?

Fusion releases more energy than fusion as the slope of the graph for fusion is steeper than fission.

Is fusion or fission more radioactive?

Fission is more radioactive than fusion

Why is Fe-56 the most stable?

Highest binding energy per nucleon and is therefore the best stuck together/stable nucleus

What does alpha radiation consist of?

Fast moving Helium nuclei

Ionisation and penetrating power of alpha radiation

Most ionising radiation but has the least penetrating power

What is alpha radiation deflected by?

Deflected by electric or magnetic fields

What do alpha particles deflect/attract?

Anything that's charged

What does beta radiation consist of?

Fast moving electrons

Ionisation and penetrating power of beta radiation

Medium ionising power and medium penetrating power

What is beta radiation deflected by?

Deflected by electric or magnetic fields

What must you never shield beta radiation with?

Lead

Why mustn't you shield beta particles with lead?

Produce x-rays as electrons strike a dense metal

Transmutation (Definition)

Where one element is changed to another

What happens in the nucleus of an atom undergoing beta radiation?

A neutron is changed to a proton and a beta particle. Beta particle is shot off

What does gamma radiation consist of?

Very high energy electromagnetic waves which travels at the speed of light

Ionisation and penetrating power of gamma radiation

Least ionising ability but highest penetrating power

Can gamma radiation get deflected by electric and magnetic field?

No

Why can't gamma radiation get deflected by electric and magnetic field?

It has no charge

Explain how gamma radiation affects the nucleus of an atom

Neutrons and protons arrange themselves so that they are more tightly arranged. This leaves some extra nuclear glue/ binding energy which is released as gamma radiation

When are gamma rays emitted?

Emitted from a nucleus which has already emitted an alpha or beta particle. It results from an internal rearrangement of the nucleons. Nucleus structure remains the same but loses energy and becomes more stable

Atomic number (Definition/ calculation)

Number of protons (and usually number of electrons

Mass number (Definition/calculation)

Number of protons + Number of neutrons

How do alpha particles cause harm?

Once it enters a substance it rips electrons from neutral atoms creating ions. This causes harm.

What happens to the negative electrons left after the alpha particle rips other electrons?

Attract the positive alpha particles and slows them down until they stop

How do beta particles cause harm?

They cause less ionisation but penetrate further. They repel electrons out of shells.

What causes beta particles to be really dangerous?

High concentration is what causes beta particles to be dangerous

Why do gamma rays have the least ionisation?

They are uncharged

Effect of gamma ray's low ionisation

Makes them difficult to detect

Numbers of gamma rays

Large number

How do gamma particles cause harm?

Removes electrons from the substance hit by hitting at electron to remove it

Draw a diagram of an alpha particle hitting an atom (Before and After)

Draw a diagram of a beta particle hitting an atom (Before and After)

Draw Half life Vs Radioactivity

Radioactivity (Definition)

The spontaneous disintegration of unstable nuclei with the emission of one or more types of radiation. It is unaffected by physical or chemical processes/changes

Who discovered by radioactivity?

Henry Becquerel

Half-life (Definition)

Of an element is the time taken for half of the nuclei in any given sample to decay

Half-life (Activity Definition)

Of an element is the time taken for half for the activity of any given sample to decrease to half of its original value

Decay constant (Definition)

The proportion of the number of atoms that decay per second

Decay constant unit

s⁻¹

Law of radioactive decay (Activity formula)

A = dN / dt or A = -λN

Law of radioactive decay (Activity formula/calculation)

A = λN

What is A (Law of radioactive decay)?

Activity

What is activity/radioactivity activity measured in?

Bq

What is N (Law of radioactive decay)?

Number of nuclei in sample

What is λ (Law of radioactive decay)?

Decay constant

1 Becquerel = … disintegration per second

1

Half life formula

T1/2 = Ln2 / λ

What is T1/2? (half-life formula)

Half-life

What is λ? (half-life formula)

Decay constant

Einstein's mass-equivalence equation

E = mc²

What is E? (Einstein's mass-equivalence equation)

Energy

What is m? (Einstein's mass-equivalence equation)

Mass

What is c? (Einstein's mass-equivalence equation)

Speed of light

Name 4 health hazards of ionising radiation

Radiation burns. Genetic mutations. Cancer. Death

Environmental radiation (Definition)

The effect of ionisation radiation on humans depends on the type of radiation (gamma most harmful externally alpha most harmful internally). The activity of the source in Bq. The time of exposure. The type of tissue irradiated.

Sources of background (ionising) radiation

Granite/Radon. Medical & Dental X-Rays. Airline Flights

Explain Granite/Radon (Background radiation)

Found from rocks releasing radiation. Can be trapped under buildings. Pipes built under to carry it out and to air

Explain Airline Flights (Background radiation)

Long haul flights by more x-rays as higher up means less air density means getting hit by more x-rays from space at a higher risk of cancer

Precautions when handling radioactive sources (3)

Should never be handled directly. Should not eat or drink in their vicinity. Should be stored in a shielded secure place

Uses of ionising radiation (10)

Curing cancer. Medical tracers. Smoke alarms. Dating organic material. Dating rocks. Heart pacemakers. Measuring thickness of materials/structural defects.Industrial/agricultural tracers. Food preservation. Sterilizing surgical equip

What chemical is used to cure cancer?

Cobalt-60

Curing cancer use (Explain)

Has a short half-light and is chemotherapy when injected into the body

What chemical is used for medical tracers?

Iodine-131

Medical tracers use (Explain)

Used to check if thyroid is functioning. If there's radiation everywhere it means thyroid isn't working

What chemical is used for smoke alarms?

Americium-241

When do smoke detectors expire?

Expiry due to half-life

What chemical is used for dating organic material?

Carbon-14

What chemical is used for heart pacemakers?

Plutonium-238

What is Plutonium-238 used for in artificial pacemakers?

Power artificial pacemakers

Explain measuring thickness of materials/ structural defects

If thickness is even then constant amount of radiation will pass through. If some areas have a greater/lesser thickness then more or less radiation will pass through

Explain industrial tracers

Radioactive metal engines run and oil is checked for radiation to check for friction. The more friction makes it less fuel efficient

Explain food preservation

Radiation beamed to kill bacteria and fungi before shipping e.g. strawberries

Explain the sterilisation of surgical equipment

Equipment placed in bag and radiation beamed to kill microorganisms

Name a detector of ionising radiation

Geiger-Müller tube

Draw a Geiger-Müller tube

Explain a Geiger-Müller

When radiation enters the tube it ionises some of the Br2 molecules. The positive ions are attracted to the case and the negative ions are attracted towards the wire. Gas amplification occurs. When this charge reaches electrodes it passes arounf the external circuit as a pulse of current. This produces a potential difference across the series resistor and is used to operate a counting device.