Radioactivity Flashcards
What does a nucleus atom contain?
- Protons and Neutrons
- makes up Mass of the atom
- doesn’t take up space because it’s TINY
Atomic number / proton number
number of protons in nucleus
Mass number
Total number of protons and neutrons in a nucleus
Electrons
-negative charge
-really small
-whizz around outside of atom
-paths take up a lot of space
Atoms are neutral so…
No. Protons = No. Electrons
Define Isotopes
Atoms with the same number of protons but different number of neutrons (diff mass no.)
Each element only has..
1-2 stable isotopes
Radioactive isotopes
-nucleus is unstable➡️decays and emits radiation
Unstable nuclei:
break down at Random
Nucleus decay
-Spontaneously in its own time
-unaffected by temperature/chemical bonding
-when nucleus does decay it splits out 1or more types of radiation (alpha, beta, gamma, neutrons)
-nucleus often changes to new element
Nuclear radiation causes ionisation by…
-Bashing into atoms and knocking electrons off of them
-atoms to ions➡️ionisation
Ionisation pattern
Further the radiation can penetrate before hitting an atom and getting stopped, the less damage it will do along the way = less ionising it is
What can be used to to detect ionising radiation
-Geiger-Müller detector
-photographic film
Alpha particles
-2 protons 2 neutrons
-big heavy, slow moving
-don’t penetrate far into materials
- stopped quickly
Why do alpha particles create lots of ions
Because of big size - strongly ionising - bash into a lot of atoms & knock electrons off
Are alpha particles positively charged or negatively
-Positively - deflected by electric/magnetic fields
-emitting alpha particle decreases atomic number of nucleus by 2 and mass number by 4
Define Beta particles
electron emitted from nucleus of atom when neutron turns into proton/electron
What happens when a beta particle is emitted
Number of protons in nucleus increases by 1 - atomic number increases by 1, mass number stays same
Beta particles moving
-FAST and small
Beta particles penetrating
Penetrate moderately before ionising
Are beta particles charged positively or negatively?
Negatively- deflected by electric and magnetic fields
Gamma rays
-short wave lengths
- no mass just energy
-penetrate long way into materials without being stopped
-weak ionising - pass through rather than collide
Do Gamma rays have charge
No charge, not deflected by magnetic /electric fields
Gamma rays emissions
-Always happens after beta alpha decay
-no effect on atomic /mass number of isotope
What are alpha particles blocked by
Paper, skin, few cm of air
What are beta particles blocked by
Thin metal
What are gamma rays blocked by
Thick lead, very thick concrete
Do radioactive samples always decrease over time
Yes
Do older samples have more or less radiation
Less because the activity of an unstable nuclei decreases
Define half life
Time taken for activity to fall by half
* short half life activity falls quickly
* long half life falls more slowly
Beta and gamma will penetrate the skin and other body tissues this makes them suitable for…
Medical tracers
What can radiation treat
Cancer: ionising radiation can kill/damage cells, but once cancer started then ionising radiation an be used to react as well
RADIOTHERAPY
-Kills cancer cells stops dividing
-high doses of gamma rays
Gamma rays and sterilising equipment
Irradiation: Food and medical equipment can be irradiated with high doses of gamma rays to kill microbes without damaging food/ equipment (not high temperatures)
Radiation used in industry for tracers and thickness gauges
Detects leaks in under pipes
What is beta radiation used for
Thickness control
Ionising radiation damaging cells and tissues
Beta and gamma penetrate the skin AND soft tissues to reach delicate organs -more HAZARDOUS
Risks for alpha radiation
-Cannot penetrate skin
-do all their damage in very localised area
How does radiation damage cells
Collides with molecules- more exposure more damage
What do lower doses of radiation cause to us
Minor damage - can cause mutations - cells divide uncontrollably - cancer
Objects near a radioactive source are ———— by it
Irradiated
Ways to reduce risk of irradiation
-keep sources in lead lined boxes
-standing behind barriers
-being in different room
- remote controlled arms
What is contamination
Radioactive particles getting onto objects
What happens when atoms are contaminated
- decay releases radiation which may cause harm - very dangerous if enters body
How to prevent contamination
Use gloves, tongs, protective suits, masks
Is radioactive waste easily disposed safely
No
Where is low level radioactive waste from nuclear power stations and hospitals disposed
Clothing, syringes buried in secure landfill sites
How do we dispose of high level radioactive waste
-It is really dangerous- since it stays highly radioactive for tens of thousands of years
-sealed into glass blocks then sealed in metal canisters then buried deep under ground
- geologically stable place
What do nuclear power stations use
Nuclear FISSION chain reaction
Define Nuclear Fission
Splitting of atoms that release energy -eg. Uranium-235
Neutrons released by fission reactions in a nuclear reactor have a lot of energy. How are these absorbed by uranium nuclei and sustain the chain reaction?
Need to be slowed down by a moderator: Graphite, Water which slows down neutrons
What limits the rate of fission
Control rods made of boron by absorbing excess neutrons
High energy neutrons and gamma rays are released in fission are highly penetrating ionising radiation what absorbs the ionising radiation?
Shielding: thick concrete structure containing lead or other metals
What is nuclear FUSION
OPPosite of nuclear FISSION: 2 nuclei collide at HIGH speed and FUSE to create a larger heavier nucleus.
Does the heavier nucleus have more mass
Not as much as the 2 separate nuclei did. some lighter nuclei are converted into energy and released
Does FUSION release a lot of energy?
Yes, all the energy released in stars come form fusion
What is the big problem with fusion only happening in…
Really high temperatures since positively charged nuclei have to get really close to fuse so they move really FAST to overcome force from ELECTROSTATIC REPULSION
