All matter is made up of atoms (which are basic particles)
Atoms have a small nucleus consiting of protons (+ charged ) and neutrons (neutral). The nucleus is surrounded by electrons (-)
The mass number (or nucleon number) of an element is the total number of protons and neutrons in the nucleus of an atom.
The atomic number (or proton number) of an element is the number of protons (or electrons) in the nucleus of an atom.
All atoms of a particular element have the same number of protons. The number of protons defines the element.
However, some atoms of the same element can have different numbers of neutrons - these are called isotopes. oxygen has three isotopes oxygen-16, oxygen-17 and oxygen-18
some substances contain isotopes with unstable nuclei. An atom is unstable when its nucleus contains too many or too few neutrons.
Unstable nuclei split up or disintergrate, emitting radiation. The atoms of such isotopes disintergrate randomly and are said to be radioactive. There are three main types of radioactive radiation- Alpha, Beta, Gamma.
A radioactive isotope will emit one of the three types of radiation from its nucleus...
Activity- is the average number of disinergrations that occur every second-measured in becquerels.
Half life of a radioactive isotopes...
is a measurement of the rate of radioactive decay. (the time it takes for half the nuclei to decay.)
If a radioactive isotope has a very long half life, then it remains active for a very long time.
It can be used to date certain materials by measuring the amount of radiation they emit- materials which can be dated include-
- very old samples of wood
- remains of prehistoric bones
- certain types of rock
Radiation and Ionastion...
when a substance emits radiation it collides with neutral atoms of molecules in a substance, the atoms or molecules may become charged due to electrons being 'knocked out' of their structure the collsion. This alters their structure, leaving them as ions or charged particles.
IONISING RADIATIONS-include Alpha particles, beta particles and gamma rays (they are randomly emitted from the unstable nucleus nuclei of radioactive isotopes.)
Ionising radiation can damage cancer cells and tissues causing cancer or mutations (changes) in the cells and the result of deformed babies at birth. This is precautions must be taken.
Ionising radiation on Organisms cont..
If the source is outside the body...
- alpha radiaton is stopped by the skin and cannot penetrate into the body
- Beta and gamma radiation and X-rays can penetrate into the body to reach the cells of organs where they are absorbed.
If the source is inside the body...
- alpha radiation causes most damage as it is strongly absorbed by cells, causing the most ionisation.
- beta and gamma radiation and X-rays cause less damage as they are less likely to be absorbed by cells.
Ionising radiation can be used to treat tumours and cancers
Radiotherapy slows down the spread of cancerous cells.
Uses of Radiation...
- controlling the thickness of Sheet materials - the greater the thickness the greater the absorption of radiation. A beta emitter is used.
- Smoke detectors- alpha particles are used
- sterilisations of medical instruments - gamma rays are used
- preserving food-low radiation kills microorganisms and pro-longs shelf life
- Radioactive (Carbon) Dating.
Background radiation occurs naturally around us. It has no affect on our health as there is only a very small dose.
Without the atmospheric and magnetic fields, life on earth would be impossible.