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Radioactivity Flashcards

1
Q

What is radioactive decay?

A

The breakdown of the nucleus of an atom.

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2
Q

What is natural radioactivity?

A

The decay of nuclei in atoms, releasing particles and energy.

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3
Q

What is an isotope?

A

Atoms of an element that have the same number of protons but not electrons.

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4
Q

Give a reason why an atom might be radioactive.

A

Unstable Nuclei:
- Maybe the nucleus is too big or there are too many neutrons.

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5
Q

What is radiation measure with?

A

A Geiger Counter.

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6
Q

What is Background Radiation.

A

Radiation that is random and natural and occurs all around us.

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7
Q

Name the 3 types of radiation:

A

Alpha(α)
Beta(β)
Gamma(γ)

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8
Q

Identify the structure of Alpha Radiation:

A
  • Equivalent to a helium nucleus
  • Is a particle
  • 2 protons 2 neutrons
  • Positively charged
  • Mass of 4au
  • Relatively slow
  • Occurs if a nucleus is too big
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9
Q

Identify the structure of Beta Radiation:

A
  • High Speed
  • Negatively Charged
  • Negligible mass.
    Occurs if an atom has too neutrons!
  • One neutron transforms into a proton and an electron, then the electron is emitted from nucleus as Beta decay.
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10
Q

Identify the structure of Gamma Radiation:

A
  • NOT a particle
  • Electro-magnetic wave
  • Travels at the speed of light
  • Has no mass and no charge
  • NO CHANGE OCCURS WHEN RELEASED FROM NUCLEUS!
  • emitted after beta and gamma.
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11
Q

What is the chemical representation of alpha decay:

A

-4 off atomic mass and -2 off atomic number to get product of an element after alpha decay. (2 protons, 2 neutrons)

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12
Q

What is the chemical representation of beta decay:

A

Take nothing off atomic mass and add one to the atomic number. Beta decay is represented as B with a 0 at the top and a -1 at the bottom.

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13
Q

What is the chemical representation of Gamma decay:

A

Just the symbol don’t change the numbers at all.
+ (γ)

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14
Q

Order Beta, Alpha and Gamma in there ability to penetrate. Then say Why:

A
  1. Gamma (Best and Penetrating)
    - Worst at ionising (longest time to lose energy)
    - Stopped by lead or concrete.
  2. Beta (Mid Penetrating power)
    - Medium ionising power (Loses energy fairly quickly)
    - Stopped by aluminium
  3. Alpha (Worst Penetrating Power)
    - Good at ionising (Loses energy very fast)
    - Stopped by a piece of paper or even air
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15
Q
A
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16
Q

Between 2 plates charged positively and the other negatively where would the particle/radiations go?

A

The Beta (overall - charge) would go to the positively charged plate quickly.
The Gamma (neutral charge) would go straight through not leaning towards either plate
The Alpha (overall + charge) would lean towards the negatively charge plate but take longer to get there than Beta.

17
Q

What is ionising Radiation?

A

Particles or waves that cause atoms to lose or gain electrons and become charged.

18
Q

What is the half-life?

A

Average time taken for half a sample of radioactive substance to decay (or for the activity to halve)

19
Q

What does “the activity” mean?

A

The number of decays per second.

20
Q

{Carbon dating is a process used to determine the age of dead organic materials.} -C14 has a half life of 6000 years.
Scientists are studying a mammoth found frozen in ice. They find a sample of carbon from the remains that has a count rate of 200Bq. The scientists work out that when the mammoth died the count rate was 800Bq. Use this information to calculate how long ago the mammoth died.

A

800Bq 🡢 400Bg 🡢 200Bq
- 2 half lives
2 × 6000 = 12000 years ago.

21
Q

What happens to a radioactive source the older it gets?

A

The activity decreases = less radiation emits.
(how quickly the activity decreases is DIFFERENT for each isotope)

22
Q

Describe the Ionising power of Alpha:

A
  • Turning a neutral atom into a charged ion
  • Alpha ionises the easiest (It has the biggest charge) 2+
  • Alpha can attract nearby electrons from further away.
23
Q

Describe the Ionising power of Gamma

A
  • Worst at ionising
  • No charge
  • Needs to come in direct contact with an electron to cause ionisation (very rare).
24
Q

Describe the Ionising power of Beta:

A
  • Less easily than alpha (more easily than gamma as it has charge) (smaller charge) 1-
  • Beta will repel an electron from a nearby atom to ionise it.
25
Q

What is countrate?

A

The number of ionizing events detected by a radiation detector per unit of time.

26
Q

What does Bq Stand for? What are they?

A

Becquerels
- A unit that measures radioactivity.

27
Q

Name the Eight uses of Radioactivity:

A

1) Automatic Thickness Monitoring
2) Medical tracers
3) Uranium Dating
4) Carbon Dating
5) Killing cells
6) Smoke Detectors
7) Fault Tracers

28
Q

Explain Automatic Thickness Monitoring:

A
  • Used in factories to control the thickness of materials
  • If materials too thick = more radiation absorbed = less reaches detector
  • If material is too thin = less radiation absorbed= more reaches detector.
  • Detector sends signal to adjust rollers accordingly.
29
Q

Explain Medical Tracers:

A
  • Trace a flow of substance through a system.
    -e.g. see if patients kidneys are blocked.
  • Patient drinks radioactive substance.
  • Detector is placed on the outside of the patients body to monitor flow.
  • Radioactive substance must be emitters of Beta or Gamma because:
  • Short half life wont stay in body too long and cause harm.
  • Alpha particles cannot penetrate skin.
30
Q

Explain Uranium Dating:

A
  • Finds age of rocks
  • Uranium decays into lead
  • Half life of Uranium = 4.5 billion years.
    -Ratio of uranium to lead helps to estimate age.
31
Q

Explain Carbon Dating:

A
  • Carbon 14 is an isotope that decays into Carbon 12 (stable)
    -When an organism dies it stops taking in Carbon 14 so it begins to decay into Carbon 12
  • Time since organism died can be worked out by measuring the amount of C14 left vs Starting amount.
32
Q

Explain Killing Cells:

A
  • Gamma radiation used
    . High energy + High frequency causes cells to die
  • kills cancer cells, sterilise medical equipment, kill food bacteria.
  • When radiation enters a living cell 2 things can happen:
    -high does =kill cell
    -low doses =cause cancer
33
Q

Explain Smoke Detectors:

A
  • Within smoke detectors there is = Americium (Alpha radiation source)
  • Since Alpha particles are charged it ionises the air causing a current to flow between 2 charged plates.
  • Smoke particles absorb alpha particles and neutralize the ions decreasing the current
  • This decrease causes alarm to sound.
    ALPHA used because will not escape and harm people.
34
Q

Explain Fault Tracers

A
  • Radioisotopes used for tracking substances
  • Finds leaks or blockages underground in pipes
  • Gamma often used because it can pass through many substances.
    To find the blockage/leak:
  • Radioactive material put into one end of the pipe
  • Radiation detector above ground tracks its process.
  • Leak/Blockage detected where radiation changes.
    Places there’s a leak = Higher count Rate.
35
Q

Outline Ernst Rutherford’s Gold foil experiment:

A

-Alpha particles shot at gold foil in experiment from a radioactive source
-There was a detector surrounding an experiment that detected that some alpha particles went straight through whilst some bounced back and some deflected slightly.

36
Q

Ernst Rutherford observed that some alpha particles travelled through undeflected. What did he infer from this?

A
  • The atom is mainly empty space.
37
Q

Ernst Rutherford observed that some alpha particles were deflected by small angles. What did he infer from this?

A
  • The nucleus is positively charged and as is the alpha particle.
38
Q

Ernst Rutherford observed that some alpha particles travelled straight back from foil. What did he infer from this?

A
  • The nucleus carries most of the atom’s mass. (The nucleus has mass)

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