Radioactivity

Radioactivity

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

Non-ionising radiation

Ultraviolet ,visible ,infrared ,microwaves, radio and TV

Ionising

More dangerous ,radiation capable of producing ions (bonds broken) when interacting with matter ,x-rays ,alpha ,beta Gamma ,cosmic rays

Pierre and Marie curie

Purified pitchblende

Discovered Polonium and Radium

Studied radiation to uranium

Which elements are radioactive?

Most elements have radioactive isotopes but any element with an atomic number greater than 83 consists entirely of radioactive isotopes

Uranium is the heaviest natural occurring element. Most elements above 92 are artificially created in nuclear research facilities.

3 types of radiation

Alpha beta gamma

Alpha particles

Consists of 2 protons and 2 neutrons —helium nucleus

Attracted to - charge so positive

Thrown out by unstable radioactive nuclei until they become stable

Relatively large mass -slow -not very penetrating -stopped by air or a sheet of paper -not dangerous as they can’t penetrate skin

Americium-241 is used in smoke alarms

Beta particles

Attracted to + charge so negative

Fast moving/high energy electrons

Formed when a neutron is changed into a proton and electron ,and electron is ejected from the nucleus

More penetrating -pass through paper and up to 5mm of aluminium

Carbon-14 emits beta particles so is used for carbon dating

Gamma rays

High energy electromagnetic radiation-similar to x-rays

Passed straight through electric and magnetic fields so not charged

very penetrating -only stopped by tick layer of lead

very dangerous carcinogenic

Can be used to cure cancer and sterilise surgical instruments

Cobalt 60 is used in radiotherapy/killing tumours

Nuclear reaction

Radiation emitted from the nucleus. Completely different from chemical reactions.

Difference between chemical and nuclear reactions

Chemical

1. No new element formed

2. No release of nuclear radiation

3. Chemical bonds broken and formed

   Nuclear reaction

4. A new element is formed

5. Nuclear radiation is released

6. No new chemical bonds broken or formed

What happens to radium 226 when it emits an alpha particle

Ie. Loses 2P and 2N

Mass number decrease by 4 to 222 because 4 nucleons lost

Atomic number decrease by 2 to 86 because 2 protons lost

Changes to element two places before it

What happens to carbon 14 when it loses a beta particle

Mass stays same

Atomic number decreases by 1

Changes to an element 1 after it in the periodic table

Eg alpha

Eg beta

Transmutation

The changing of one element to another

Half-life

The time taken for half of the nuclei of an element to decay

Radioisotope

Radioactive isotope eg. Americium 241, Carbon 14, Cobalt 60