Chapter 8 - Radioactivity Flashcards
What did Pierre and Marie Curie discover?
Radioactivity carried an electrical charge
Isolated two new elements POLONIUM & RADIUM
Who discovered radioactivity?
Henri Becquerel
Define radioactivity
Spontaneous emission of one or more types of radiation,alpha,beta and gamma from unstable nuclei
What are Alpha particles?
Positively charged rays. Consist of 2 protons and 2 neutrons, i.e helium nuclei 4He
Penetrating ability and effects of Alpha particles?
Not very penetrating - stopped by a sheet of paper or 5 cm of air.
Effects - damaging to the DNA in cells - cause cancer
What are Beta particles?
They are negatively charged rays. Occur when a neutron in an unstable nucleus is changed into a proton and an electron and this electron is EJECTED from a nucleus. (Give example)
Penetrating ability of Beta particles?
Moderately penetrating - stopped by 5mm of aluminium
What are gamma particles?
Neutral rays unaffected by electrical fields.
Gamma rays are High energy photons. -example - cobalt
Gamma particle penetrating ability?
Very penetrating. Only stopped by a thick block of lead.
What is transmutation?
When a new element is formed when alpha and beta particles are emitted.
Chemical reactions VS Nuclear reactions
Chemical reactions deal with ELECTRONS being transferred or shared. The nuclei of the atoms stays the same.
Nuclear reactions only deal with the change in the NUCLEUS resulting in the formation of a new element.
Nuclear fission
Large nuclei break up to form two smaller ones releasing a large quantity of energy.
Nuclear fusion
Light nuclei join together to make a heavier one releasing energy.
Define Half Life
The TIME taken for HALF of the nuclei in any given sample to DECAY
What is a radioisotope?
A radioactive isotope
Outline 3 uses of Radioisotopes
1) Medicine: radiotherapy- gamma rays from cobalt 60 are used to kill cancerous tissue.
2) Food Irradiation: irradiation with gamma rays kills pathogenic organisms in food causing no loss of flavour. Not suitable for all foods such as red meats etc as they turn brown.
3) Industrial uses: Am 241 is used in smoke detectors.
Equation for alpha particles
226 Ra —- ??? + ?
88
226 Ra —- 222 Rn + Alpha
88 86
- 4 from larger number of atom
- 2 from smaller number
The new element + alpha
Beta particle equation
14C —- ??? + ?
6
14C —- 14N + B
6 7
Larger number stays the same
Smaller number - +1
Gamma ray equation
60CO — 60CO + Y
Stays the same but add a Y
