P-4 Atomic Structure Flashcards
- How big are atoms
- 1 x 10(-10) meters radius
- What is the basic sctuture of an atom
- Positively charged nucleus of protons and neutrons surrounded by negatively charged electrons
What is the radius of a nucleus
- Less than 1/10000 of radio of Atom
Where is most of the mass of an atom
-In the nucleus
How are electrons arranged
- Arranged at different distances from nucleus in shells
How does electrons arrangement change with absorption of electromagnetic radiation
- higher energy levels cause them tome further away from the nucleus
How doe Electron arrangement change with emission of electromagnetic radiation
- Lower energy levels causes them to go closer to the nucleus
What is the relationship between protons and electrons in an atom
- They are the same
What is a proton number
- All atoms in an element have the same number of protons
- This number of protons is called the proton number
What is the mass number
- Number of protons and neutrons added together
- What are isotopes
- Atoms of the same element with a different number of neutrons
- Usually only one or two stable ones
- What happens ion atoms loose one or more outer shell electrons
- They turn positive
- How may a scientific model be changed
- Experimental evidence
What were atoms thought to be before electrons were discovered
- Tiny spheres that couldn’t be divided
- What did the discovery of the electron lead to
- The plumb using model
- What did Rutherford’s scattering experiment conclude
- The plumb pudding model could not be true
- Beam of alpha particles aimed at gold foil
- Deflected - only positive
- Couldn’t be true
What did Bohr say
- Electrons orbit at certain distances called energy levels- this agreed with experimental evidence at the time
What lead to the discovery of protons
- Later experiments led to idea that positive charge of any nucleus could be subdivided into smaller equally charged particles called protons
What lead to the discovery of the neutron
- The experimental work of James Chaswick provided evidence for Neutron- 20 years after nucleus
What is radioactive decay
- Some atom nuclei are unstable
- The nucleus gives out radition as it changes to become more stable
- This is called radioactive decay
- What is activity
- The rate at which radioactive material decays- measured in Bq
What is count rate
- Number of decays each second detected by a detector
What are the qualities of Alpha particles
- Two neutrons, two protons
- Travel a few cm though air
- Absorbed by paper
- Strongly ionising
- What are the qualities of Beta particles
- High speed electrons from nucleus
- Travel a few meters through air
- Absorbed by aluminium
- Moderately ionising
- What are the qualities of Gamma
- Electromagnetic radiation from nucleus
- Kms range in air
- Absorbed by thick wall of concrete
- Weakly ionising
What are nuclear equations
- Used to represent radioactive decay
How may alpha and Beta be shown
- Alpha-
4
2 He
Beta-
0
-1 e
What amy the emission of radiation cause
- A change in mass or charge
- 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
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
What does gamma decay cause
- No change
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
What is the nature of radioactive decay
- It is random
What is radioactive contamination
unwanted presence of materials containing radioactive atoms on other material;s
What is the hazard of radioactive decay determined on
- Type of radiation and rate
What is irradiation
- Proces of exposing an object to radiation
- Does not become radioactive itself
- Often kept behind bars
What is the risk of each type of radiation on the outside of the body
- Gamma and Beta high
_Alpha - high
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
