Physics Radioactivity

Define the term radiation

The emission and transfer of energy through space or a medium

What is the mass number

The number of an element which tells us the number of neutrons plus protons of the element

What is the atomic number

The number of an element which tells us the number of protons of the element

What is the charge of an atom

neutral (no. of protons = no. of electrons)

What is the charge and relative mass of protons

Charge= +1 and mass is 1

What is the charge and relative mass of neutrons

C= 0, M=1

What is the charge and relative mass of electrons

C= -1 , M= 0.00005

How much smaller is an electron than protons and neutrons

2000x

What are isotopes

atoms of the same element that have the same number of protons but varying number of neutrons

What is the process radioactive decay

It is the process when unstable isotopes of elements decay intro other elements by emitting radiation (alpha, beta or gamma) or sometimes just emitting neutrons.

Describe what electron excitation is and why that releases energy in what form

When an atom absorbs energy (from heat or light), an electron can jump from a lower energy shell to a higher one (called excitation). The excited electron in the higher energy shell will eventually fall back down (because it would be unstable) and when it does, it releases energy in the form of EM radiation

What is ionisation

It is when an atom absorbs so much energy that the outermost electron will completely leave the atom, leaving it with a positive charge making it a positive ion. This is ionising radiation, a type of radiatuon that carries enough energy to remove electrons from the atoms, turning them into ions.

What is ionising Radiation

A type of radiation that has enough energy to remove electrons from atoms, causing ions

What does it mean if a material is radioactive?

It contains unstable isotopes that can decay (emit radiation)

What is another name for ionising radiation

nuclear radiation, this is because, when unstable atoms release energy to become stable, that energy often comes from changes happening inside their nucleus and "Nuclear" refers to anything that comes from or involves the nucleus of an atom.

What are the 4 types of ionising radiation?

• Alpha Radiation

• Beta Particles

• Gamma Rays

• Emission of a neutron

Describe the structure of an alpha particle and why its often referred to as Helium (He)

Alpha particles are made up on 2 neutrons and 2 protons that comes from the nucleus of an unstable atom. This is often referred to as a helium particle as it has the same make up. They also have an overall charge of 2+

Describe the ionisng and penetrating power of alpha particles

Alpha particles are highly ionising due to their large mass and size. But they are the weakest in penetrating meaning they can only travel a few cm in air and are easily absorbed by a single piece of paper

Describe the structure of beta particle and how its made

Beta particles are just electrons, but they are made when an atom's neutron decays into a proton and electron. The proton stays in the neutron, but the electron is emitted at high speeds.

Describe the ionising and penetrating power of beta particles

Beta particles are moderately ionising and moderatly penetrating. For example, it would travel several meters in air but is stopped by 5mm of aluminium to stop. Beta particles are also less ionsing than alpha radiation as they are smaller.

What are gamma rays

electromagnetic waves that are often emitted after alpha or beta particles as a way of the nucleus getting rid of extra energy

Describe the ionisng and penetrating power of gamma radiation

Gamma rays are the most penetrating as they have no mass or charge and can therefore pass straight through materials. It takes thick pieces of lead or multiple layers of concrete to stop them. Gamma rays are however the least ionising.

Describe what emission of a neutron is

it is when a nucleus has too many neutrons (making it unstable), it can throw out a neutron to increase its stability

How do u do a nuclear decay equation for alpha particles

Using the example of Uranium-238

1. The Uranium 238 mass number will minus 4

2. The atomic number of uranium 238 will minus 2

3. Because the result will have a different atomic number, use the periodic table to find the new element

4. to the new element as He- 4 (2 atomic number)

How do u write the nuclear decay equation for beta decay

for example using C-14

1. The mass number of carbon stays the same but the atomic numnber gains 1

2. find out the new element and add e- 0 (M) and 1 (A)

How do u write the nuclear decay equation for gamma radiation

for thorium-234

It will be the same it will be th 234 → th 234 + gamma ray

How do u write the nuclear decay equation for neutron emission

for example Be 9

1. The mass number of Be 9 loses 1 but teh atomic number stays the same (same element therefroe)

2. So Be 9 would equal Be 8 + a neutron (1 and 0)

Define the term activity

a samples overall rate of decay

What is activity measured in

Becquerels (1 Bq = 1 decay per second)

What are the two definitions for half-life

1. The time taken for the no. of radioactive nuclei in a sample to half

2. The time taken for the no. of decays, or activities to half

Explain the graph of activty by time

This is because as time goes on the number of particles remaining and activity of the sample will decline. the rate of decline will also fall as shown through the curve

What instrument is used to measure activity in real life and how does it work

a geiger- muller tube and counter. The instrument records all the decays that reach them each second

Define the term irradiation

the process by which objects are exposed to radiation

Define the term contamination

When radioactive particles get onto or into other objects

What are the three factors that determine how harmful radiation is

1. Type of Radiation

2. Where you’re exposed to it

3. The amount

Why is beta and gamma radiation harmful to you and not alpha when its outside of the body

This is because beta and gamma radiation can penetrate through the skin and thorugh tissues to reach vital organs. Alpha radiation however cannot penetrate through and harm u when outside the body

What is the most harmful type of radiation and why

Ionising radiation because they enter living cells and interact with the molecules inside. It can ionise our DNA and cause mutations (cancer)

What is the most dangerous type of radiation when the source is inside the body

alpha

What does the dosage of radiation depend on

• How far from the source you are

• how long you’re exposed

• how radioactive the substance is

What are some precautions you can take whilst being around a radioactive source

1. Wearing gloves and overalls

2. Handling the radioactive material with tongs

3. Keeping the radioactive material in a lead lined box

Where can you find low level radioactivity and how do you dispose of it

• in clothes and syringes

• disposed by burying in secure landfill sites

Where can you find intermediate level radioactivity and how do you dispose of it

• found in nuclear reactors, radioactive sources in medicine

• disposed by burying it in concrete

Where can you find high level radioactivity and how do you dispose of it

• found in nuclear fuel and chemical waste

• disposed by encasing it in concrete and burying it deep underground

What are for uses for nuclear radiation

• Medical tracers

• Radiotherapy

• Sterilisation

• Industry

How do medical tracers works

• a source that emits beta or gamma radiation is injected into the patient

• As the source moves around the body, it can be detected using a radiographer

• doctors use this method to check whether vital organs are working as they should be

• the radioactive soruce has to have as short a half-life as possible so they only emit radiation for a short period and stop being harmful

How does radiotherapy work

high doses of radiation can be used to kiss cancer cells and stop them divided. Gamma rays are used

How does steriliastion work

food and medical equipment can ve irradiated with a high dose of gamma rays to kill all microbes

How is nuclear radiation used in industry

gamma emitting tracers are used to detect leaks in underground pipes. a crack in the pipe will show extra high radiation. use short half life

Define nuclear fission

The division of a large and unstable nuclei into a smaller nuclei (with the release if energy) and neutrons

What is spontaneous fission and how often does it happen

when fission occurs by itself (is unforced), rare

What is the process of nuclear fission in a nuclear reactor (4)

1. A slow moving neutron is fired at an unstable nucleus like uranium-235

2. The unstable nucleus absorbs the neutron and splits into two daughter nuclei and 2-3 nuetrons whilst emitting energy in the form of gamma radiation

3. The 2-3 nuclei that were released are then absorbed by other unstable nuclei and the process repeats creating a chain reaction

4. The gamma radiation released is used to boil water into steam which turns turbines, converting kinetic energy into electricity by a generator

Why is it important that nuclear chain reactors are kept under control

to avoid a nuclear meltdown.

What are pros of nuclear energy

• The uranium fuel is relatively cheap

• it produces a large and steady amount of energy

• doesn’t produce greenhouse gases

What are cons of nuclear energy

• The powerplant itself is very expensive to build

• the produced nuclear waste is expensive to dispose

• theres always a risk of major disaster (alck of public support)

what is the purpose of control rods in a nuclear reactor

absorb neutrons and slow down the fission process

what is the purpose of containment building in a nuclear reactor

absorb dangerous radiation

what is the purpose of the moderator in a nuclear reactor

slows down the neutrons so that it can be absorbed by the unstable nuclei

what is the purpose of fuel rods in a nuclear reactor

contains the uranium for fission

Define the process of nuclear fusion and give examples

when two lighter nuclei, join to form a single larger nuclei. an example is 2 hydrogen nuclei fusing together to form a single helium nuclei

why is nuclear fusion beneficial

• it releases alot of energy (from some of the mass of the original two nuclei) and fuels stars

• It is how all elements heavier than hydrogen are made

• it doesn’t produce any nuclear waste

why is nuclear fusion not done on earth

because it only happens at really high temperatures and pressures for it to overcome the repulsion of a positively charged nucleus

Describe the uses of radioactivity in household smoke alarms

• An alpha source ionises air between 2 electrodes causing a constant current. Smoke blocks the alpha so tthe he current stops

What is carbon dating

The determination of an organic matter by finding the amount of carbon-14 that it contains

Describe the logic behind how carbon dating works

• All living organisms absorb carbon, carbon -12 (stable) and carbon -14 (unstable)

• when an organism dies, it stops absorbing carbon

  • The carbon - 12 stays the same

  • the carbon-14 begins to decay and reduces

• Scientists can use the ratio of carbon-12 to carbon-14 in an organism to find its age

what is the equation for the formation of a carbon-14 isotope

¹⁴N + ₀¹N → ¹⁴C + ₁¹P

What is the equation for the decay of carbon-14

¹⁴C → ¹⁴N + Beta radiation