P2 Radiation & LifeLesson 3: Ionisation

Starter Which 3 things affect radiation

intensity?

Starter Which 3 things affect radiation

intensity?The distance from the sourceThe type and frequency of radiationThe number of photons

Objectives MUST understand what is meant

by ionising radiation SHOULD understand how

ionisation occurs COULD understand that exposure

to ionising radiation can damage living cells

Atoms Atoms are made up of a nucleus

containing protons and neutrons and electrons which wizz around the outside

Neutrons are neutral Protons are positively

charged Electrons are negatively

charged

Key Words You need to be able to define the

following:› Electron› Atom› Molecule› Ion› Ionisation› Ionising radiation› Mutation

Neutral Atoms and Molecules

Normally atoms and molecules have a neutral charge

They have an equal number of protons and electrons

For example a helium atom has two protons and two neutrons

Ionisation Ions are charged atoms or molecules Atoms or molecules can be charged if

their numbers of protons and electrons are unequal

Ions can be formed by “knocking out” electrons from atoms or by breaking molecules apart

This process of forming ions is known as Ionisation

Ionisation Radiation that can cause ionisation is known as

ionising radiation

Ionising radiation is found at the high frequency end of the electromagnetic spectrum because they carry the most energy

The three types of electromagnet radiation that are ionising are: UV, X-rays, and Gamma Rays

Textbook Answers1) Ions are charged and atoms are not; ions are

charged and molecules are not. 2)a) Positive; b) negative3)An atom absorbs an X-ray photon. An electron is

knocked out of the atom. A positive ion is formed.4)The photons of radio waves do not carry enough

energy to cause ionisation; gamma photons do.5) Ionisation in the body is a problem because it

changes molecules in cells and so changes processes in cells, e.g. causing cancer, or even the death of the cell.

6)Gamma radiation; it is the most energetic form.