Radioactivity

Detection of radioactivity 

Background radiation: the small amount of radiation around us all the time because of radioactive materials in the environment. It mainly comes from natural sources such as soil, rocks, air, building materials, food and drink – and even space.
•Detection:
Alpha particles – the cloud chamber:
A chamber has cold alcohol vapour inside it. The alpha particles make the vapour condense, so you see a trail of tiny droplets. It is useful because it makes the tracks visible.

Alpha, Beta and Gamma – the Geiger-Müller (GM) tube
The “window” end is thin enough for alpha particles to pass through. If an alpha particle enters the tube, it ionizes the gas inside. This sets off a high-voltage spark across the gas and a pulse of current in the circuit. A beta particle or gamma radiation has the same effect. It can be connected to a ratemeter (tells the counts per seconds), a scaler (tells the total number of particles or bursts of gamma radiation) or an amplifier or loudspeaker (makes a click for every particles/burst of radiation.

Characteristics of three kind of emissions 

Radioactive decay

Radioactive decay: A radioisotope (an unstable arrangement of neutrons and protons in a nucleus) is altered to make a more stable arrangement. The parent nucleus becomes a daughter nucleus and a particle (decay products). Words and symbol equations using examples:
•Alpha decay:
An element with a proton number 2 lower and nucleon number 4 lower, and an alpha particle is made (2p + 2n) e.g.
Words: Radium-226 nucleus (parent nucleus) → Radon-222 (daughter nucleus) + helium-4 nucleus (alpha particle)
Symbols:22 a 222 n 2 e
•Beta decay:
A neutron changes into a proton, an electron and an antineutrino so an element with the same nucleon number (just 1 neutron is now a proton but the mass is the same) but with a proton number 1 higher e.g.
Words: iodine-131 nucleus → xenon-131 nucleus + antineutrino + beta particles (electron)
Symbols: (antineutrino symbol = v with a horizontal line on top of it)
•Gamma emission:
With some isotopes, the emission of an alpha or beta particle from a nucleus leaves the protons and neutrons in an “excited” arrangement. As the protons and neutrons rearrange to become more stable, they lose energy. This is emitted and the mass and atomic number are uncharged.
Gamma emission by itself causes no change in mass number or atomic number.

Half life 

Half-life of a radioisotope: is the time taken for half the nuclei present in any given sample to decay.
Some nuclei are more stable than others.

Safety precautions 

Ionising radiation can break molecules into smaller fragments. These charged particles are called ions. Ions can then take part in other chemical reactions in the living cells. As a result, ionising radiation damages substances and materials, including those in the cells of living things.

radioactive stuff is stored in a lead container, in a locked cabinet
•picked up with tongs, not your feet
•kept away from the body, not pointed at people
•left out of its container for as short a time as possible