Topic 4 Atomic Structure Flashcards
1
Q
What can electrons do if they gain energy by absorbing EM radiation?
A
Move to higher energy level- further from nucleus
2
Q
What can electrons do if they emit/release EM radiation?
A
Move to lower energy level- closer to nucleus
3
Q
What does EM radiation stand for?
A
Electromagnetic
4
Q
What is radioactive decay?
A
Unstable nuclei decay to become more stable, emitting radiation in process
5
Q
What is ionising radiation?
A
Knocks electrons off atoms, creating positive ions
6
Q
What are the 4 things a nucleus can emit in radioactive decay?
A
Alpha particle
Beta particle
Gamma ray
Neutron
7
Q
What is alpha radiation?
A
alpha particle emitted from nucleus
8
Q
What is an alpha particle?
A
2 neutrons and 2 protons (same as helium nucleus)
9
Q
What is the ionising power of alpha particles?
A
Strongly ionising
10
Q
What is the penetrating power of alpha particles?
A
Absorbed by skin/paper
11
Q
How far can alpha particles travel in air?
A
< 5cm
12
Q
What is the symbol for an alpha particle?
A
a
13
Q
What is a beta particle?
A
Fast moving electron released by nucleus
14
Q
What is the ionising power of a beta particle?
A
Moderately ionising
15
Q
What happens every time a beta particle is emitted from a nucleus?
A
Neutron turns into proton
16
Q
What is the penetrating power of a beta particle?
A
Absorbed by 3mm aluminium foil
17
Q
How far can beta particles travel in air?
A
Metre/a few metres
18
Q
What is a gamma ray?
A
Wave of electromagnetic radiation emitted from nucleus
19
Q
What is the ionising power of a gamma ray?
A
weakly ionising (pass through rather the collide with atoms)
20
Q
What is the penetrating power of a gamma ray?
A
Absorbed by lead/concrete
21
Q
How far can a gamma ray travel in air?
A
> kilometre
22
Q
What are nuclear equations used to represent?
A
Radioactive decay
23
Q
What form are nuclear equations written in?
A
Atom before decay > atom after decay + radiation emitted
24
Q
What is the symbol for a gamma ray?
A
y
25
What is the **symbol** for a **beta particle**?
**B**
26
What **2 things happen** when an **atom emits an alpha particle**?
**Atomic number reduces** by **2**
**Mass number reduces** by **4**
27
What does **alpha decay cause** the **mass** and the **charge** of a **nucleus to do**?
**Decrease**
28
How is an **alpha particle written** in **nuclear equations**?
As a **helium nucleus**
29
What happens to the **number of protons** in the **nucleus** when **beta decay occurs**?
**Increases by 1**
30
What happens to the **charge** of the **nucleus** when **beta decay occurs**?
**Increases**-
31
Why does the **mass** of the **nucleus not change** when **beta decay occurs**?
**Neutron lost** but **proton gained- same mass**
32
How is a **beta particle written** in **nuclear equations**?
As an **electron**
33
What happens to the **atomic number** when **beta decay occurs**?
**Increases by 1 (proton gained)**
34
What happens to the **charge** and **mass** of the **nucleus** when a **gamma ray is emitted**?
**No change**
35
What **type of process** is **radioactive decay**?
**Random**
36
What is **count-rate**?
**Number of decays recorded each second** by a **detector**
37
What is the **name of the detector** that **records count-rate**?
**Geiger-Muller tube**
38
What is **activity**?
**Rate** at which **source of unstable nuclei decays**
39
What is **activity measured in**?
**Becquerels Bq**
40
What is **background radiation**?
**Low-level radiation** around us **all the time**
41
What are **2 things background radiation comes from**?
**Natural resources**
**Man-made sources**
42
What are **2 examples** of **natural resources** that are **sources of background radiation**?
**Cosmic rays** from **space**
**Rocks**
43
What are **2 examples** of **manmade sources** of **background radiation**?
**Fallout** from **nuclear weapons testing**
**Nuclear accidents**
44
What does **radiation dose tell you**?
**Risk of harm** to **body tissues** due to **radiation exposure**
45
What is **radiation dose measured in**?
**Sieverts (Sv)**
46
What **2 things** does the **level of background radiation** and **your radiation dose depend on**?
**Occupation** and **location**
47
What is **irradiation**?
**Exposing** an **object** to **nuclear radiation**
48
What does **irradiating something not do**?
Make it **radioactive**
49
What are **2 ways** of **reducing the effects of irradiation**?
**Keeping sources** in **lead-lined boxes**
Standing behind **barriers**
50
What is **radioactive contamination**?
**Unwanted material containing radioactive atoms** on **other materials**
51
Why is **contamination harmful/hazardous**?
**Contaminating atoms decay, releasing radiation**
52
What are **3 ways of protecting against contamination**?
**Gloves**
**Using tongs**
**Wear protective suits**
53
How does **wearing a protective suit prevent contamination**?
**Prevents breathing in particles**
54
How does **using gloves and tongs prevent contamination**?
**Avoids particles getting stuck** to **skin/under nails**
55
What does the **level of hazard/harm** of **contamination or irradiation depend on**?
**Type** of **radiation emitted**
56
Which **2 radiation sources** are **most dangerous outside the body (irradiation)**?
**Beta** and **gamma**
57
Why are **beta** and **gamma** the **most dangerous outside the body**?
**Penetrate body** and get to **delicate organs**
58
Why is **alpha less dangerous outside** of the **body**?
**Can’t penetrate skin** and **easily blocked**
59
When is **irradiation dangerous from all sources**?
**High levels**
60
Which **type of radiation** is **most dangerous inside the body (contamination)**?
**Alpha**
61
Why is **alpha the most dangerous inside the body**?
**Most ionising**, causes **damage** in **very localised area**
62
Why is it **so important** that **research into the effects of radiation on humans** is **published** and **peer-reviewed**?
Become **quickly accepted**, **improve our use** of **radioactive sources**
63
What is the **risk of radiation entering living cells**?
**Ionise atoms/molecules** within cells- **tissue damage**
64
What is **risk** of **lower doses** of **radiation**?
Cause **minor damage without killing cells**, lead to **cancer (mutant cells divide uncontrollably)**
65
What is the **risk** of **higher doses** of **radiation**?
**Kill cells completely**, causes **radiation sickness**
66
What are **3 symptoms** of **radiation sickness**?
**Vomiting**
**Tiredness**
**Hair loss**
67
What **2 things** are **nuclear radiations** **used in medicine for**?
**Exploration** of **internal organs**
**Destroying unwanted tissue (treating cancer)**
68
How can **internal organs** be **explored** using a **tracer**?
**Radioactive isotopes injected/swallowed**, their **progress around body** followed using **external detector**
69
What is **treating cancers** using **ionising radiation known as**?
**Radiotherapy**
70
Why can **high doses** of **ionising radiation** be used to **treat cancers**?
**Kill all living cells**
71
How are **gamma rays used** to **treat cancer**?
**Directed into body** and **kill cancer cells**
72
What are the **2 ways** of **treating cancer using radiation**?
- **external gamma rays**
- **internal radiation-emitting implants**
73
How can **radiation emitting implants** be **used to treat cancer**?
**Put next to/inside tumours**
74
What is the **advantage** of **treating cancer** using **radiation-emitting implants**?
**Targets tumour very precisely**- **less damage** to **healthy tissue**
75
What is the **disadvantage** of using **external gamma rays** to **treat cancer**?
**Fair amount** of **damage** to **healthy tissue- patient feels ill**
76
What is the **perceived risk**?
**How risky a person thinks something is**
77
What **type of radioactive isotopes** are usually used in **medical tracers**?
**Gamma sources**
78
What are the **2 things radioactive isotopes entering the body should have**?
**Pass out body** without causing much **ionisation**
**Short half life** so **radioactivity quickly disappears**
79
What is an **example** of a **radioactive isotope** used to **explore internal organs**?
**Iodine-23**, show whether **thyroid gland taking in iodine**
80
What are **medical tracers used for**?
**Exploration of internal organs**
81
What is **nuclear fission**?
**Splitting** of a **large** and **unstable nucleus**
82
What are **2 examples** of **large unstable atoms**?
**Uranium**
**Plutonium**
83
What is **nuclear fission used for**?
**Release energy** from **large unstable atoms** by **splitting** into **smaller atoms**
84
What is **rare (nuclear fission)**?
**spontaneous (unforced) fission**
85
What **usually has to happen for fission to occur**?
**Unstable nucleus absorb neutron**
86
What does a **nucleus undergoing fission split into**?
**2 smaller nuclei, roughly same size**
87
What do **all fission products have**?
**Kinetic energy**
88
What **3 things** are **emitted** when a **nucleus splits**?
**2 or 3 neutrons**
**Gamma rays**
**Energy**
89
How can the **neutrons emitted in fission** go on to **start a chain reaction**?
If **neutrons moving slow enough, absorbed** by **another nucleus, more fission** occurs
90
What is the **amount of energy produced by fission** in a **nuclear reactor controlled by**?
**Changing how quickly chain reaction can occur**, using **control rods**
91
How are the **control rods** used to **control the energy released in fission**?
**Lowered** and **raised** in **nuclear reactor**
92
How do **nuclear weapons work**?
**Uncontrolled chain reactions** quickly lead to **lots of energy released** as **explosion**
93
What is **nuclear fusion**?
**2 light nuclei collide** at **high speed** and **join** to create **larger, heavier nucleus**
94
What is an **example of nuclear fusion**?
**Hydrogen nuclei fuse** to **produce helium nucleus**
95
What **happens** to **some of the mass** of the **lighter nuclei** in **nuclear fusion**?
**Converted to energy and released**
96
Why have **scientists not yet found a way of using fusion** to **generate energy for us to use**?
**Temperatures** and **pressures needed so high** that **fusion reactors very hard** and **expensive to build**
97
What do **radioactive isotopes** have a **very wide range of**?
**Half lives**
98
What **happens each time** a **radioactive nucleus decays** to become a **stable nucleus**?
**Activity as whole decreases**
99
What is the **half life**?
**Time taken** for **number of radioactive nuclei** in **isotope** to **half**
100
Why do we use **half life**?
**Activity never reaches zero, measure how quickly activity drops of**
101
What is the **other definition** of **half life**?
**Time taken for activity/count rate to halve**
102
What does a **short half life mean**?
**Nuclei very unstable** and **rapidly decay**
103
Why are **sources** with a **short half life dangerous**?
**High amount of radiation emit at start, quickly become safe**
104
What does a **long half life mean**?
**source releases small amounts of radiation for long time**
105
Why are **sources** with a **long half life dangerous**?
**Nearby areas exposed to radiations for (millions of) years**
