P-4 Atomic Structure Flashcards
1
Q
- How big are atoms
A
- 1 x 10(-10) meters radius
2
Q
- What is the basic sctuture of an atom
A
- Positively charged nucleus of protons and neutrons surrounded by negatively charged electrons
3
Q
What is the radius of a nucleus
A
- Less than 1/10000 of radio of Atom
4
Q
Where is most of the mass of an atom
A
-In the nucleus
5
Q
How are electrons arranged
A
- Arranged at different distances from nucleus in shells
6
Q
How does electrons arrangement change with absorption of electromagnetic radiation
A
- higher energy levels cause them tome further away from the nucleus
7
Q
How doe Electron arrangement change with emission of electromagnetic radiation
A
- Lower energy levels causes them to go closer to the nucleus
8
Q
What is the relationship between protons and electrons in an atom
A
- They are the same
9
Q
What is a proton number
A
- All atoms in an element have the same number of protons
- This number of protons is called the proton number
10
Q
What is the mass number
A
- Number of protons and neutrons added together
11
Q
- What are isotopes
A
- Atoms of the same element with a different number of neutrons
- Usually only one or two stable ones
12
Q
- What happens ion atoms loose one or more outer shell electrons
A
- They turn positive
13
Q
- How may a scientific model be changed
A
- Experimental evidence
14
Q
What were atoms thought to be before electrons were discovered
A
- Tiny spheres that couldn’t be divided
15
Q
- What did the discovery of the electron lead to
A
- The plumb using model
16
Q
- What did Rutherford’s scattering experiment conclude
A
- The plumb pudding model could not be true
- Beam of alpha particles aimed at gold foil
- Deflected - only positive
- Couldn’t be true
17
Q
What did Bohr say
A
- Electrons orbit at certain distances called energy levels- this agreed with experimental evidence at the time
18
Q
What lead to the discovery of protons
A
- Later experiments led to idea that positive charge of any nucleus could be subdivided into smaller equally charged particles called protons
19
Q
What lead to the discovery of the neutron
A
- The experimental work of James Chaswick provided evidence for Neutron- 20 years after nucleus
20
Q
What is radioactive decay
A
- Some atom nuclei are unstable
- The nucleus gives out radition as it changes to become more stable
- This is called radioactive decay
21
Q
- What is activity
A
- The rate at which radioactive material decays- measured in Bq
22
Q
What is count rate
A
- Number of decays each second detected by a detector
23
Q
What are the qualities of Alpha particles
A
- Two neutrons, two protons
- Travel a few cm though air
- Absorbed by paper
- Strongly ionising
24
Q
- What are the qualities of Beta particles
A
- High speed electrons from nucleus
- Travel a few meters through air
- Absorbed by aluminium
- Moderately ionising
25
- What are the qualities of Gamma
- Electromagnetic radiation from nucleus
- Kms range in air
- Absorbed by thick wall of concrete
- Weakly ionising
26
What are nuclear equations
- Used to represent radioactive decay
27
How may alpha and Beta be shown
- Alpha-
4
2 He
Beta-
0
-1 e
28
What amy the emission of radiation cause
- A change in mass or charge
29
- What does alpha decay cause and what i s an example
- Alpha decay causes both a change in mass and charge to decrease
219 214 4
86 Randon ----- 84 Polonium + 2 He
30
What does beta decay cause
- Beta does not cause a change to mass but does cause charge to increase
14 14 0
6 Carbon + 7 Nitrogen + -1 e
31
What does gamma decay cause
- No change
32
What is half rate
- Half rate is amount of time it takes for half number of nuclei to be present tor half the count rate
33
What is the nature of radioactive decay
- It is random
34
What is radioactive contamination
unwanted presence of materials containing radioactive atoms on other material;s
35
What is the hazard of radioactive decay determined on
- Type of radiation and rate
36
What is irradiation
- Proces of exposing an object to radiation
- Does not become radioactive itself
- Often kept behind bars
37
What is the risk of each type of radiation on the outside of the body
- Gamma and Beta high
| _Alpha - high
38
What is the risk of each type of radiation on the inside of the body
- Alpha highest- Act on specific area
- Beta- low
- Gamma - none
