Radioactivity

Henri Becquerel discovered Radioactivity.

Pierre and Marie Curie discovered polonium and radium.

The nature of Radioactive Radiation

Radioactivity is the spontaneous decaying of unstable nuclei with the emission of one or more types of radiation.

There are 3 types of radiation: Alpha(α), Beta (β) and Gamma (γ)

Alpha Particles

Groups of 2 protons+ 2 neutron stuck together

Represented as ⁴2He

Alpha particles have a relatively large mass⇒slower

Low penetrating power⇒stopped by sheet of paper

E.g Americium 241- used in smoke detectors

Since Alpha particles cannot penetrate skin, they dont present an external hazard, however if inhaled/ingested they can be very harmful to interal organs.

Beta Particles

Beta particles are simply fast moving electrons.

Formed when a neutron, in a unstable nucleus changes to a proton and electron, which is then ejected.

Beta particles are lighter so travel faster.

E.g Carbon 14- used in carbon dating

More penetrating power⇒stopped by 5mm of aluminium

Gamma Particles

Gamma radiation is simply high energy electromagnetic radiation (travels at speed of light)

Doesn't contain charged particles

An unstable nucleus emits gamma radiation in order to lose surplus energy.

High penetration (most dangerous)⇒ stopped by thick slab of lead

E.g Cobalt 60-used to kill cancer cells

Nuclear Reactions

Nuclear rection is a process that alters the composition, structure or energy of an atomic nucleus.

Transmutation is the changing of one element into another and only occurs in nuclear reactions.

Chemical Reaction	Nuclear Reaction
1. Involves electrons rather than nucleus	1. Changes take place in nucleus and electrons not involved
2. No new element formed	2. New element formed
3. No release of nuclear radiation	3. Nuclear radiation is released
4. Chemical bonds broken and formed	4. No chemical bonds breaking or bonds formation involved

Calculating Alpha Particles 

226           222         4
       Ra→      Rn +   He      
 88             86           2

→minus 4 from mass number of original element (Ra)

→minus 2 from atomic number of original element (Ra)

→on periodic table find element that has matching atomic number (86= Radon, Rn)

Calculating Beta Particles 

14        14       0
    C→     N +   e     
  6         7        -1

→dont change mass number of original element (C)

→add 1 onto atomic number of original element (C)

→on periodic table find element that has matching atomic number (7= Nitrogen, N)

Half lifes

It has been found that each radioactive isotope (radioisotope) decays at its own rate,

The half life of an element is the time taken for half of the nuclei in any given sample to decay