T Level Radiation Recap

Radioactive Decay

Unstable Nuclei

Some atoms have stable nuclei.​

​

Some atoms have unstable nuclei.​

These undergo radioactive decay to try and become more stable.

Multiple Choice

What is an isotope?

• An atom with the same number of neutrons and electrons, but a different number of protons.

• An atom with the same number of protons and electrons, but a different number of neutrons.

• An atom with the same number of neutrons and protons, but a different number of electrons.

Unstable Nuclei

The nuclei of an atom can be unstable for three reasons.

1. the nuclei is too big

- these emit an alpha particle

2. the nuclei has an incorrect ratio of protons and neutrons

- these emit a beta particle

3. the nuclei has too much energy.

- these emit gamma rays

Alpha Particles

Alpha particles (α) consist of 2 neutrons and 2 protons (no electrons).

This is the same as a helium nucleus.

Alpha decay causes the mass number of the nucleus to decrease by four and the atomic number of the nucleus to decrease by two.

The overall charge of an alpha particle is +2.

Beta Particles

If a nuclei has too many neutrons, a neutron will turn into a proton and emit a fast-moving electron. This electron is called a beta (β) particle.

A beta particle has a relative mass of zero. Beta decay causes the atomic number of the nucleus to increase by one and the mass number remains unchanged.

The charge of a beta particle is -1.

Gamma rays

After emitting alpha/beta particles, nuclei still have a high amount of energy and need to 'cool down'.

So, often they will emit gamma rays (γ). These are electromagnetic (EM) waves.

Gamma ray emission causes no change in the number of particles in the nucleus meaning both the atomic number and mass number remain unchanged.

Multiple Choice

which type of decay is also referred to as a helium nuclei?

• alpha

• beta

• gamma

Multiple Choice

Which type of decay is a type of electromagnetic wave?

• alpha

• beta

• gamma

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Chernobyl Disaster 1986

During 1986, a nuclear power plant in Ukraine experienced a critical failure in their safety measures. This resulted in a considerable amount of radioactive contamination.

This contamination included alpha, beta and gamma radiation.

Today, tourists can enter limited parts of Chernobyl.

Geiger-Muller counter

All types of radioactive decay can be detected by a Geiger-Muller tube, or G-M tube.

The radiations ionise the gas inside and the resulting charged particles move across the chamber and get counted as charges rather like an ammeter.

Geiger Counters Video Link

Open Ended

Tourists at Chernobyl must wear miniature versions of GM counters - why is this a good idea?

Ionising and Penetrating Power

Ionising Power - to ionise means to convert an uncharged atom or molecule into a charged particle by adding or removing electrons.

Penetrating Power - the power of the radiation that demonstrates how far into a material the radiation will go.

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Multiple Choice

How ionising is alpha decay?

• low

• moderate

• high

Multiple Choice

how penetrating is beta decay?

• low

• moderate

• high

Multiple Choice

how ionising is gamma radiation?

• low

• moderate

• high

Types of Radioactive Emission

Alpha Decay

• Radiation through the loss of 2p + 2n or

(helium)

Beta Decay

• Radiation where a neutron splits, giving off

an electron and becoming a proton in the
new element

Multiple Choice

Alpha particles (alpha decay) are comprised of

• 2 Protons & 2 Neutrons

• 4 Neutrons & 2 Electrons

• an electron

• an energy wave

Multiple Choice

Beta particles (Beta decay) are comprised of

• 2 Protons & 2 Neutrons

• 4 Neutrons & 2 Electrons

• an electron

• an energy wave

Question 3a

Balance the nuclear equation after alpha
decay

Question 3a

Balance the nuclear equation after alpha
decay

Question 3b

Balance the nuclear equation after beta decay

Remember in beta decay a neutron changes into a proton by giving off an
electron

Question 3b

Balance the nuclear equation after beta decay

Remember in beta decay a neutron changes into a proton by giving off an
electron

Multiple Choice

Balance the following equation:
¹⁴₆C --> ⁰_-1e + ________

• ¹⁴₅B
• ¹⁴₆C
• ¹⁴₇N
• ⁴₂He

Multiple Choice

If Gadolinium-150 goes through alpha decay, the resulting element has a new atomic mass of _____.

• 150
• 148
• 146

Multiple Choice

If we start off with element ⁵⁰₂₄X after an gamma decay we get an element(product) that looks like...

• ⁵¹₂₄X

• ⁵⁰₂₃X

• ⁵⁰₂₄X

• ⁵⁰₂₅X

Multiple Choice

Uranium-238  decays into  Thorium-234  by emitting .........

• an alpha particle
• a beta particle
• gamma rays
• visible light

Multiple Choice

If we start off with element ₂₄X⁵⁰ after an alpha decay we get another element Y that looks like

• ₂₂Y⁵⁰
• ₂₂Y⁴⁶
• ₂₀Y⁴⁸
• ₂₆Y⁵⁴

Multiple Choice

²⁴⁰₉₄Pu —› ____ + ⁴₂He

• ²³⁶₉₂U

• ²⁴⁷₉₆Cm

• ²⁴⁴₉₃Np

• ²⁴²₉₅Am

Half Lives

​What is it?

the time taken for half of the nuclei to decay

Some radioisotopes have long half lives, like U-238, and some have short ones, like I-131. Long half lives can be used to date ancient artefacts. Carbon-13 is useful in this instance. Short half-lives are useful in medicine.

Let's count!

​If you have 100g of a radioactive isotope, how much would you have after two half-lives-

a) if the half life is 3 years?

b) if the half life is 3 hours?

Multiple Choice

A radioisotope has a half-life of 10 years. In the year 2000, there was 50g of this sample in a container. How much would there be in the year 2020

• 25g

• 12.5g

• 100g

Multiple Choice

The half life of plutonium is 24300 years. If nuclear bomb released 8kg of this isotope, how many years would pass before the amount is reduced to 1kg?

• 72900

• 50

• 8100

• 5

Exponential Decay

​trendlines in science

Trendlines are used to make clear the trend in the data

You can have linear and non-linear trends

Non-Linear trends can be exponential, logarithmic, quadratic or trigonometric

Linear trends- well, they are just straight line!

Here is a non linear exponential decaying trend

​Here is one that seems to be periodic

Radioactive Decay

Radioactive decay is an exponentially decaying function

It is a rapidly decreasing function

But a very useful function because we can determine the half life of these radioactive isotopes

Which experiment had a longer half life?

​

Multiple Choice

Determine the amount of the radioisotope left 4 years

• approx 60g

• approx 6g

• approx 155g

• 10g

Multiple Choice

Determine the half life or radioisotope 'x'

• approx 5 years

• approx 1 year

• approx 1/2 year

• approximately 50 years

Can we use half life to predict amounts?

Suppose we start with 120 atoms of a radioactive sample, how many will remain after three half lives?

What percentage is that?

The half life of Carbon-14 is 5730 years. You have a sample that has only 25% of the original amount. How many years has passed?

Radioactive Dating

In 1896, Marie and Pierre Curie worked with Henri Becquerel to study the element Uranium. Together, they discovered the property of radioactivity, which is used in a variety of technologies and sciences.

What is Radioactive Dating?

• Igneous Rocks naturally contain some radioactive elements

• Scientists can measure the amount radioactive elements in a rock and compare it to the half-life of those elements

Ohio Grade 8 | Lesson 6.3

Potassium-Argon Dating

• How scientists often date rocks

  • Used due to a very long half-life

• When Potassium-40 breaks down, it forms argon-40

  • has a half life of 1.3 Billion Years

Ohio Grade 8 | Lesson 6.3

Carbon-14 Dating

• Carbon-14 is a radioactive form of carbon

  • Has a half life of only 5,730 years

• All plants and animals have carbon

  • After a plant or animal dies, Carbon-14 decays into nitrogen-14

• Only good for fossils younger than 50,000 years old

  • after that the amount of carbon is too small to be measured

Ohio Grade 8 | Lesson 6.3

Multiple Choice

Scientists use the method of _________ to find the absolute age of a rock

• radioactive dating

• relative dating

• Carbon-dating

• lava dating

Multiple Choice

True or False: Carbon-14 is used for dating fossils because it has a short half life

• True

• False

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Fission and Fusion

Nuclear Fission

• ​Larger nuclei break down into smaller more stable nuclei.

• A lot of Energy is released.

• Source of all Nuclear Power on Earth.

• e.g. Nuclear Bomb, Nuclear Power Plant.​

Multiple Choice

This is an example of...

• Fission  reaction
• Fusion reaction
• Decomposition reaction
• Combustion

Nuclear Fusion

• ​Smaller nucleii combine to form larger nucleii

• Lot of Energy is released.

• Needs High Temperature and Pressure.

• Not Possible on Earth.​

  Sun and Stars - Nuclear Fusion

• e.g Hydrogen Bomb.​

The Sun

• a massive ball of plasma.  

• It is constantly burning so hot that hydrogen is fused together to form helium.

• This happens at such a rate that a huge amount of energy is released.

Multiple Choice

When small nuclei are exposed to intense heat and pressure, they join to create a larger nucleus, releasing huge amounts of energy

• Nuclear Fusion

• Nuclear Fission

Multiple Choice

The sun (or any star)

• Nuclear Fusion

• Nuclear Fission

Multiple Choice

Fission is --

• fusing together

• division

Categorize

Options (16)

Atom is divided

Two atoms join

Nuclear waste is an issue

Uses uranium and other radioactive elements

1000 x stronger

Typically uses hydrogen

Naturally occuring on the sun

Produces energy in stars

Requires high temperature and pressure

Produces helium as a byproduct

Experimental energy source

Generates heat and electricity

Used in nuclear power plants

Produces radioactive isotopes

Chain reaction can occur

Requires controlled environment

Organize these options into the right categories

Nuclear Fission

Nuclear Fusion

Multiple Choice

Which of the following is an example of nuclear fusion? 

• A plutonium atom is used to start a chain reaction that detonates a nuclear weapon 
• A uranium atom is split apart into lighter elements
•  Two hydrogen atoms are combined to form a helium atom
• Two hydrogen atoms bond with an oxygen atom to form a water molecule 

Multiple Choice

___________ starts the fission of a uranium atom.

• Energy

• Protons

• One Neutron

• All of the above

Nuclear Weapons

• Atomic Bombs use uncontrolled fission reactions

• Thermonuclear (hydrogen) bombs use fission reactions to induce fusion - 100x more powerful than atomic bombs

Multiple Select

Which of the following correctly display nuclear fission?

Multiple Select

Which of the following correctly display nuclear fusion?

Multiple Choice

What is true about nuclear fusion? 

• The mass of the product is less than that of the original nucleus
• The mass of the product is 100 times less than that of the original nucleus
• The mass of the product is the same as that of the original nucleus
• The mass of the product is greater than that of the original nucleus

Multiple Choice

Which of the following is true about nuclear fission?

• The mass of the product is greater than the mass of the original nucleus
• The mass of the product is less than that of the original nucleus
• The mass of the product is the same as the mass of the original nucleus
• The mass of the product is 100 times greater than the original nucleus

| STEM

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