Chapter 8 - Radioactivity

who discovered radioactivity

Henri Becquerel discovered radioactivity by noticing that urnamium salts caused shadows to appear on photographic plates

Who were the first people to isolate and purify the radioactive elements polonium and radium

Marie Curie and Pierre

Radioactivity

Radioactivity is the spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation

Radiation detection

a geiger counter

Types of radiation

alpha, beta, gamma

Alpha radiation

- Consist of two neutrons and two protons (helium)

- Alpha particles have a double positive charge

- Relatively large mass so they travel the slowest compared to the other two types

- Least penetrating/ paper can stop it

Beta radiation

_ They are not fast moving electrons

- Formation a neutron is an unstable nucleus changes into a a proton and an electron. The electron is ejected from the nucleus

- The neutron changes to proton + electron

- Beta particles are higher than alpha particles so travel faster + penetrative

What can Beta radiation

can penetrate up to 5mm

gamma

High energy electromagnetic radiation

- Does not consist of charged particles it is not deflected in electric or magnetic fields

- Very high penetrating power abilites omly stopped by thick lead

- Most dangerous as it is cancerous

chemical vs nucleus

1) Involves nucleus rather than electrons vs 1) Charge takes place electrons

2) No new element vs 2) New element

3) No realise nucleur vs 3) nucleur radioactive

4) Chemical bonds broken + fprmed vs 4) No chemical bond breaking/ bond formation

alpha nuclear equation

A/Z

Half life

The half life of an element is the time taken for half the new nuclei in a sample

Radioiotopes use

- Alpha: americum 24 used in smoke detectors half life 423

- Beta: Carbon 14 (half lie 5730)

- Gamma: Cobalt 60 radiotherapy 527 yrs

transmutation

changing one element into another