Radioactivity Flashcards
What is radioactive decay?
The breakdown of the nucleus of an atom.
What is natural radioactivity?
The decay of nuclei in atoms, releasing particles and energy.
What is an isotope?
Atoms of an element that have the same number of protons but not electrons.
Give a reason why an atom might be radioactive.
Unstable Nuclei:
- Maybe the nucleus is too big or there are too many neutrons.
What is radiation measure with?
A Geiger Counter.
What is Background Radiation.
Radiation that is random and natural and occurs all around us.
Name the 3 types of radiation:
Alpha(α)
Beta(β)
Gamma(γ)
Identify the structure of Alpha Radiation:
- Equivalent to a helium nucleus
- Is a particle
- 2 protons 2 neutrons
- Positively charged
- Mass of 4au
- Relatively slow
- Occurs if a nucleus is too big
Identify the structure of Beta Radiation:
- High Speed
- Negatively Charged
- Negligible mass.
Occurs if an atom has too neutrons! - One neutron transforms into a proton and an electron, then the electron is emitted from nucleus as Beta decay.
Identify the structure of Gamma Radiation:
- NOT a particle
- Electro-magnetic wave
- Travels at the speed of light
- Has no mass and no charge
- NO CHANGE OCCURS WHEN RELEASED FROM NUCLEUS!
- emitted after beta and gamma.
What is the chemical representation of alpha decay:
-4 off atomic mass and -2 off atomic number to get product of an element after alpha decay. (2 protons, 2 neutrons)
What is the chemical representation of beta decay:
Take nothing off atomic mass and add one to the atomic number. Beta decay is represented as B with a 0 at the top and a -1 at the bottom.
What is the chemical representation of Gamma decay:
Just the symbol don’t change the numbers at all.
+ (γ)
Order Beta, Alpha and Gamma in there ability to penetrate. Then say Why:
- Gamma (Best and Penetrating)
- Worst at ionising (longest time to lose energy)
- Stopped by lead or concrete. - Beta (Mid Penetrating power)
- Medium ionising power (Loses energy fairly quickly)
- Stopped by aluminium - Alpha (Worst Penetrating Power)
- Good at ionising (Loses energy very fast)
- Stopped by a piece of paper or even air
Between 2 plates charged positively and the other negatively where would the particle/radiations go?
The Beta (overall - charge) would go to the positively charged plate quickly.
The Gamma (neutral charge) would go straight through not leaning towards either plate
The Alpha (overall + charge) would lean towards the negatively charge plate but take longer to get there than Beta.
What is ionising Radiation?
Particles or waves that cause atoms to lose or gain electrons and become charged.
What is the half-life?
Average time taken for half a sample of radioactive substance to decay (or for the activity to halve)
What does “the activity” mean?
The number of decays per second.
{Carbon dating is a process used to determine the age of dead organic materials.} -C14 has a half life of 6000 years.
Scientists are studying a mammoth found frozen in ice. They find a sample of carbon from the remains that has a count rate of 200Bq. The scientists work out that when the mammoth died the count rate was 800Bq. Use this information to calculate how long ago the mammoth died.
800Bq 🡢 400Bg 🡢 200Bq
- 2 half lives
2 × 6000 = 12000 years ago.
What happens to a radioactive source the older it gets?
The activity decreases = less radiation emits.
(how quickly the activity decreases is DIFFERENT for each isotope)
Describe the Ionising power of Alpha:
- Turning a neutral atom into a charged ion
- Alpha ionises the easiest (It has the biggest charge) 2+
- Alpha can attract nearby electrons from further away.
Describe the Ionising power of Gamma
- Worst at ionising
- No charge
- Needs to come in direct contact with an electron to cause ionisation (very rare).
Describe the Ionising power of Beta:
- Less easily than alpha (more easily than gamma as it has charge) (smaller charge) 1-
- Beta will repel an electron from a nearby atom to ionise it.
