Lecture notes
RADIACTITVITY
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Lecture notes of 5 pages for the course Edexcel at Edexcel (.)
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RadioactivityBecquerel → unit of radioactivity
Centimeter → unit of length
Hour, minute, second → unit of time
bigger number is the mass number (proton+neutron)
smaller number is the atomic number (number of proton)
symbol is the Element Symbol
Isotope: are atoms of the same element with the same proton number and different neutron
number
An atom is radioactive because their are too many neutrons in the nucleus which makes it unstable,
the unstable nucleus will emit radiation so it helps it become stable
Radioactive decay: unstable element decay into other elements by emitting radiation
3 types of radiation:
- Alpha
- Beta
- Gamma
- Emit neutrons
Alpha:
- A heavy nucleus emits an alpha particle
- It has a helium nucleus (2 neutrons 2 protons)
- Stopped by a sheet of paper
- Highly ionizing
- Weekly penetration (large particles)
- Take 4 off the mass number
- Take 2 off the atomic number
- If alpha enters it causes mutation, cancer
, Beta:
- A neutron turns into a proton and emits a beta particle (electron)
- Fast moving electrons
- Negative charge
- Much smaller mass than alpha
- The smaller mass makes it:
- less highly ionizing than alpha
- less penetrating than gamma
- Stopped by thin sheet of aluminum
Mass number stays same
Atomic number goes up by 1
Gamma:
- Waves Electromagnetic spectrum
- Emitted after alpha or beta radiation so the nucleus gets rid of energy
- High frequency
- Weakly ionizing
- Highly penetrating
- Can be stopped by thick lead or concrete
Ionising means: potential to gain or lose electron
Penetrating means how far the radiation travels before it stops
Emitting neutrons:
- If there are too many neutrons (unstable
- It throws out neutron
- To increase stability
- Subtract 1 from mass number
Activity: rate of decay of all the isotopes in the sample
OR
The number of decays that occurs per unit time
1 Bq = 1 decay per second
Half life: is the time taken for the number of radioactive nuclei in a sample to halve
OR
The time taken for the number of decays or activity to halve
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