radioactivity

protons - positive charge, mass 1, is equal to the atomic number , nucleus of atom
neutrons - no charge, mass 1, proton + neutron numbers = mass number, nucleus of atom
electrons - negative charge, negligible mass (1/1836), found in shells in a neutral atom no. of protons = no. of neutrons i.e. charges balance out

Atoms of the same element with the same atomic number but different mass numbers i.e. different numbers of neutrons

A random process in which unstable nuclei lose energy by emitting radiation

Equal to the number of particles emitted per second from a radioactive source
Activity decreases over a period of time and is measured in Becquerels

The emission of ionising radiation or particles caused by the spontaneous disintegration of atomic nuclei. The random process throws out unstable nuclei to make the nucleus as a more stable. (in istopes) measured in Bq

- radiation that reaches Earth from space - and from radioactive isotopes in the soil, rocks and air. Artificial sources include radioactive waste from nuclear power stations or medical x-rays

- helium nuclei released
- alpha particle consisting of 2 protons and 2 neutrons
- This decreasesthe atomic number by 2 and the mass number by 4.
- Strongly ionising
- Weak penetrating power - can travel a few centimetres in air
- Stopped by paper

- a neutron in the nucleus turns proton and electron.
- proton remains in the nucleus, high speed electron is emitted from the nucleus.
- The proton number increases by 1 but the mass number stays the same.
- Medium ionisation and penetrating power
- Stopped by thin metal (aluminium)

They are transverse waves with energy, Since it is a wave with no charge or mass, there is no effect on the atomic or mass numbers
- Weak Ionising power- Strong penetrating power
Stopped by thick lead

- remove the source to measure bg count over a time period, divide count by time period, do it 3 times, calculate mean
- then source count rate - bg count rate from all results
- Measure the count rate on a GM detector 3 times when nothing is placed between the source and the detector, calculate mean
- replace the source, insert diff materals in between, repeat 3 times, calculate mean and the subtract

the time is taken for half of the radioactive atoms in a sample to decay r
The time taken for the activity (count rate) to fall by half
Short half-life - activity falls quickly, decay quickly
long half-life - activity falls slowly, decay over long time

Tracers - ingested and absorbed in a particular part of the body. radioactivity tracked and detected externally by doctors. The tracer needs to be an isotope with a short half-life
Gamma rays - sterilize patients food, medical/surgical equipment, use irradiation, Cancer Treatment

Detect leaks in underground pipes using Geiger Muller Tube - tracer is fed into pipe, if there is a crac more radiation will be collected otside the pipe, high radioactivity there. The short half life for no long term hazards
Beta - thickness control of paper

lower dose radiation - kills cells - mutations - divisions - cancer
Higher doses - kills cells - radiation sickness

Irradation - receiving radiation from a radioactive source. Once the radiation source is removed, the radiation stops
Contamination - having radioactive atoms get onto or into an object, these atoms, might decay releasing radiation

Radioactive waste can have half-lives up to hundred of years
low-level radioactive sources are buried
high level radioactive sources-dangerous, sealed in glass blocks, then sealed in meta canisters, buried deep underground. high level must be buried in a geographically stable site, since big movements in the rock cause leakage, the material could contaminate groundwater

Keep exposure time short and wear protective clothing e.g. goggles, stand behid barriers
Store the source in a lead lined boxes
use gloves and tongs while handling tools, wear protective sits and masks to stop breathing in particles

Splitting of the nucleus to produce heat energy (power station work). slow-moving neutron absorbed by uranium 235 nucleus and causes it to split. 2 lighter daughter nuclei and another neutron is spit out. This hits another uranium nucleus - a chain reaction.

Nuclear energy (energy store) → thermal energy (heat from fission used to heat water) → kinetic (steam expands) → kinetic (steam turns turbine) → kinetic (turns generator) → electrical energy/energy is transferred electrically across power grid.

Made of graphite or water it is capable of slowing down neutrons that pass through them.

In a nuclear reactor are used to absorb excess neutrons and slow down fission. They are made of boron.

Neutrons and gamma rays released are dangerous and penetrating ionizing radiation. Shielding made of concrete absorbs the ionising radiation.

light nuclei collide at high speed to fuse to create larger, heavier nucles. Hydrogen nuclei fuse to produce a helium nucles. the creation of larger nuclei resulting in a loss of mass from smaller nuclei, accompanied by a release of energy. Energy released in stars comes from fusion

(nuclei are positively charged) In order for fusion to occur the electrostatic repulsion of protons needs to be overcome. Hence the particles need to move at very high speeds.

Splitting of atoms vs combining of atoms
Power station vs star
collision vs high temp & pressure
Nuclear Fusion Diagram