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P7-Radioactivity Flashcards

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1
Q

Atoms are very small , what is the radius of an atoms .

A

1*10to the power of negative 10

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2
Q

What is the radius of a nucleus ?

A

-Less than 1/10,000 of the atom .

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3
Q

Where is most of the mass of an atom

A

-concentrated in the nucleus .

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4
Q

What does the nucleus contain , so what is its charge ?

A

Protons postive charge , ad neutrons no charge so overall charge of nucles is positive .

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5
Q

Electrons

A

negatievly charged found at fixed energy levels form the nucleus .

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6
Q

Energy levels that are further form the nucleus …

A

are at a higher energy than those which are close to the nucleus .

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7
Q

If an atom absorbs electromagnetic radiation-light-…

A

an electron can move from a lower energy level to a higher energy level .
-An atom can now emit electromagnetic radiation , returns to the lower energy level .

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8
Q

What is the mass number?

A

number of protons and neutrons

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9
Q

What is the atomic number ?

A

protons - all atoms of an elemnt have same protons or it isn’t that elemnt .

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10
Q

What is the charge of an atom ?

A

No charge
-As the numbero f electons are = to the nuumber of protons .

(The negative charges on the electrons cancel out positive charged on the protons )

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11
Q

How do you work out the number of neutrons ?

A

Mass Number - Atomic Number .

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12
Q

What are Isotopes ?

A

-Atoms of the same elemnt thata have different number of neutrons .

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13
Q

What are ions

A

electrically charged particles formed when atoms gain or loose elctrons .
-Atoms can loose electrons from their out energy elvels .

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14
Q

Atoms loose an electron…

Atoms gains an electron

A

1+charge

1- charge

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15
Q

What did the ancient Greeks believe everything was made of ?

A
  • Evertyhing is made of atoms .

- Thought atoms were tiny spheres which cannot be divided .

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16
Q

What did scientists discover in 1897 ?

A
  • Atoms contain tiny negative particles . They are called electrons .
  • This showed atoms are not spherres that cannot be divided , atoms have an internal structure .
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17
Q

Plum pudding model :

draw ad explain .

A

-An atom is as a ball of positive charge with negative elctrons embedded in it . Check sheet .

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18
Q

Why was the Alpha Scattering experiment done ?

A

To see if the plum pudding model was correct .

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19
Q

What is the first step of the alpha scattering experiment .

A

Take a place of gold foil.

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20
Q

Why was gold foil used ?

A

-Gold foil was used s it can be hammered down into very thin foil , just a few atoms thick .

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21
Q

What is the second step of the alpha scattering experiment ?

A

Then they fired tiny alpha particles at the gold foil .

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22
Q

What was the first observation of the alpha particle experiment ?

A

-Most of the alpha particles passed straight through the foil without changing direction .

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23
Q

What was the second observation of the alpha particle experiment ?

A

-Sometimes an alpha particle was deflected .

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24
Q

What was the third observation of the alpha particle experiment ?

A

-Sometimes an alpha particles bounced straight back off the goild foil .

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25
What does the first observation suggest ?
-Atoms are mainly empty spacce .
26
What does the second observation suggest ?
-The center of the atoms must hve had a posiitve charge that repelled the alpha particles .
27
What does the third observation suggest ?
-The mass of the atom must be the concentrated center , we now call this paert of an atom the nucleus .
28
what was the final conclusion to the plum pudding model ?
-replaced with the nuclear model . Tiny positive nucleus Mostly empty space negative lectron around the edge .
29
What did Niels Bohr do ?
- Electrons orbit the nucleus at speicifc disances , his work agreed with other sicenitsts - We now call the "Orbits" energy levels or shells .
30
Wha did James Chadwick do ?
- several years later , positive chargge in nuncleus so called protons . - years after nuclar model , James Chadwick discovered neutrons , said they have no charge , are neutral .
31
Some isotopes have an unstbale nucleus , what do they do to become stable , and what is this called ?
- To become stable , the nucleus gives out radiation , this is known as radiactive decay . - Radioactive decay is a random process .
32
What is the activity ?
The activity is the rate at which a source of unstable nuclei decay .
33
What is activity measrued in ?
In Becquerel (Bq) 1Bq is = s decay per second .
34
What is the countrate ?
Is the number of deays recorded each second by a detector .
35
What are alpha particles ?
-Consist of two protons and two neutrons same as a helium nucleus .
36
What are Beta particles ?
-A beta particle is an electorn ejected from the nucleus at a very high speed.
37
How is an electrons ejected form the cenetr whne htere is no electrons in the center ?
- Beta particle formed inside the nucleus when a neutron changes into a proton and an electron . This is now ejected rom thhe nueclues and is called a beta particle .
38
What is Gamma radiation ?
-Gamma rays are a type of electromagentic radiaition from the nucleus .
39
What is the last time of radiaition sometimes given out by the nucleus ?
A neutron
40
What is the range of alpha particles ?
-Alpha particles are large , They can travel around 5 cm in air before they collide with air particles and sotp .
41
What is the range of Beta particles ?
-Can travel further than alpha particles as they smaller than em too . Can reach 15cm before stopping .
42
What is the range of Gamma radiation ?
-Travels severeal metres in air before stopping , longest range .
43
Penetrating power of alpha .
-stopped by a single sheet of paper .
44
Penetrating power of Beta .
-stopped by a few milimetries of aluminium .
45
Penetraitng power of Gamma radiation ?
-Even harde rto stop , stopped bys everal cm lead or concrete .
46
WHat is ionsiing power of radiation ?
-When radiaition collides with atoms , causes atoms to lose electrons to form ions .
47
Ionsising power of alpha
Very strongly ionsing
48
Ionsiing power of Beta
Quiet strongly ionsing
49
Ionising power of Gamma
Weakly ionising
50
What is half life ?
-half life of a radiactive isotope is the time it takes for the number of nuclei in the isotope of a sample to halve .
51
half life
short hlf lfie -fast decay to half | Lon half life - slow decay to half .
52
What is the second definiton of half life?
Half life is also the time it takes for the countrate (or activity) of a sample containing the isotope to half its inital level .
53
A radioactive isotope has a half life of 15 days and an initial countrate of 200 days per second . What is its countrate in 45 days , show full working out /
25 counts/s
54
Why is ionising radiation dangerous ?
-Ionsing radiaiton can increase hte irsk of cancer in humans .
55
What is irradiation ?
- Exposing an object to nuclear radiation (alpha , beta , gamma or neutrons ) e,g for sterilisation. - Most sterilistion can be done by heating but for substances that can't be heated use gamma radiation .
56
How do you sterilise a syringe ?
1. Object neededing to be sterilised is placed in a plastic wrapper stopping bacteria from enetering . 2.Place object near radioactive isotope tgar emits gamma radiaitoin . Lead shield protects workers . 4.Withdrawing the lead shield allows gamma radiation irradiate the object , the gamma radiaition kills any bacteria .
57
How does the obeject during sterilisation not become radioactive ?
As the object itself is not in contact with the radioactive isotope only the radiation emited from it .
58
What precautions do you have to take for each radioactvite sustances ?
*-Alpha , not very penetrating , so gloves . Beta and Gamma - more penetrative , lead apron can stop . High levels of radiation - lead walls , lead glass windows .
59
What is another way to reudce exposure to radiation ?
By monitoring radiation with a raidiation monitor , we can measure how much radiation has been recieved , cannot sotp though .
60
What is radioacitve contamination ?
- When unwated radiactive isotopes end up on other materials . - This is hazardous as radioactive toms decay and emit ionisng rdiation .
61
How hazardous is alpha radiation ?
-Alpha is strongly ionsing , easily stopped by skin as it is not very penetrative , HOwever can be dangerous if inhaled or swallowed .
62
How hazardous is Beta radiation ?
-Quet ionisng , easily penetrate skin and inot the body damage the cell and DNA .
63
How hazardous is Gamma radiation ?
Least damaging as it is weakly ionsing , can penetate the body , but is likely to pass straight thorgh you .
64
Peer review on the effects of radiation ?
- Scientists have explored the effects of radiation on human . - Studies have to be published and shared with other scientists allowing findings to be checked.
65
What is Background radiation ?
Radiaion all around us all the time .
66
Give one natural source of background radiation ?
-Rradioactive rockk - certain rocks are radiactive granite .
67
Give another natural source of background radiation ?
Cosmic rays from space - Cosmic rays are very high energy particles which travel through space and crsh into the Earth's atmospehre .
68
Give one source of manmade background radiation ?
Nuclear weapon testing - has released radiactive isotopes into the environment for decades.
69
Give another source of manmade background radiation ?
Nuclear accidents - Radioactive isotopes are released by accdients at nuclear power stations .
70
What is your exposure to background radiation influenced by ?
-Your locatin (Cornwall -rocks) and Occupation (Cabin crew , cosmic trays )
71
What is radiation dose measured in
Sievert (Sv) | -One millisievert (mSv) is 1/1000 of a Sievert .
72
What is the first use of nuclear radiation in medicine ?
-Exploring internal organs using a radioactive source to check whether an organ is funcitioning normally or if a cancer has developed .
73
What does radioacitve iodine do ?
- Radioactive iodine is a type of gamma radiatio , passes out the body , can be detected . - If the scan shows the thyroid has absorbed tooo much or too little iodine , doctors can use this to dianose pateints condtiions .
74
What is the first requirement of a radioactive tracer ?
1.The tracer must emit radiaition that can pass out the body and be detected (gamma or beta radiation ).
75
What is the second requirement of a radioactive tracer ?
2.The tracer must not be strongly ionisng , to minimise damage ot body tissues .
76
What is the third requirement of a radioactive tracer ?
-The tracer must not decay into another radioctive isotope .
77
What is the fourth requirement of a radioactive tracer ?
-The tracer must have a short-half lfie , so it is not present in the body for a long period .
78
Cancer cells ?
-Certain cancer cells can be destroyed using ionisng radiation - radiotherapy .
79
How does radiotherapy work ?
Rays pass into the body and destroy the tumour
80
Probelm with radiation on the outside ?
Healthy tissue may also be damaged as radiaition passes throguh the body .
81
Advanatge of radiation in the inside ?
Radiation is targeted very precisiely to the tumour , less damage to healthy tissue .
82
What is nuclear fission ?
- Some elements have large and unstable nucelueses . | - In nuclear fission , the nuceus of these element split , due to absorbtion of NEUTRON .
83
1. Stage of nuclear fission ?
-When uranium absorbs a neutron , this triggers the nucleus to undergo fission (split).
84
2. Stage of nuclear fission ?
- When the nucleus splits , it forms two smaler nuclei roughly euqal in size (daughter nuclei ). - Also emit two or three neutrons and gamma radiaition .
85
3.What is also released from nuclear fission .
- Energy is also released during fission , fission products have kinetic energy . - These neutrons can be absorbed by more uranium nuclei and trigger ufsion again known as a CHAIN REACTION .
86
Example of a controlled chain reaction .
-Used to release energy in a nuclear reactor .
87
Example of an uncontrolled chain reaction ?
The explosion of a nuclear weapon .
88
What is nuclear fusion ?
- Two light nuclei are joined to form a hevaier nucleus . | - Some of the mass of the nuclei can be converted into energy which is released as radiation . Not A CHAIN REACTION .
89
What is a nuclear reactor label parts of it
-where controlled fissionr eactions occur . -Control rods - control the number of neeutrons gthat start new fisisn reactions . -Fuel rolds ontin thematerial that relese energy during fisison . -eacotr is where fission occurs , releses energy to het up th emoderator for electriciy generation . -Moderator - slowd down the netrons for new fision rwactions .

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