Atomic structure

What happens when electrons absorb electromagnetic radiation

They move to a higher energy level

What is atomic number

This is the number of protons in an atom

What is mass number

This is the number of protons and neutrons in the nucleus of an atom

What are isotopes

These are the atoms of the same element with equal number of protons but different number of neutrons

What is an ion

This is an atom or group of atoms that are electrically charged

What were the findings and conclusions of Rutherford scattering model

• atoms are mostly empty space because most of the alpha particles passed straight through the gold foil

• The nuclues of the atom is positively charge because a few particles were deflected from their path but continued thought the gold foil

• The atoms contain a small heavy nucleus a small number of alpha particles rebounded

What were the features of the nuclear model

• nearly all of the mass of the atom is concentrated in the nucleus

• The nucleus is positively charged

• Negatively charged electrons orbit the nucleus at a distance

What were the deductions of bohrs model

• electrons orbit the nucleus at different distances

• The different orbit distances are known as energy levels

when was the neutron discovered

1932 by James Chadwick

What are the differences between the plum pudding and nuclear model

• In plum pudding atom is mostly positively charged dough which in nuclear model atom is mostly empty space

• In plum pudding negative electrons are distributed throughout the atoms in nuclear model negative electrons orbit the nucleus at a distance

• In plum pudding model mass of the atom is evenly distributed but in nuclear model mass is concentrated in the nucleus

What is radioactive decay

a random process that occurs when an unstable atomic nucleus breaks apart or changes, releasing radiation and creating a more stable nucleus

What is activity

This is the rate at which the unstable nuclei from a source of radiation decays

What instruments are used to detect radiation

• photographic film changes colour when exposed to radiation

• A Geiger-mullet tube

What is count rate

This is the number of decays recorded each second by a detector

What are the types of radiation

• alpha

• Beta

• Gamma

• Neutrons

Describe alpha particles

• the same as helium nucleus. Two neutrons and two protons

• Alpha particles have a charge of +2 this means they can be affected by an electric field

Describe beta particles

• they are fast moving electrons

• They are produced in nuclei when neutrons changes into a proton and electron

• They have a charge of -1 so they can be affected by an electric field

Describe gamma rays

• they are electromagnetic waves

• They have the highest energy of the different types of electromagnetic waves

• They have no charge

Describe neutrons

• they have no charge

• Found in the nucleus

What are the different properties of nuclear radiation

What are the uses of radiation

• producing electricity through nuclear fission

• Medical procedures during diagnosis

• Testing material

• Determine the age of artefacts

• Smoke detectors

• Checking the thickness of material

How are alpha particles used in smoke detectors

• the alpha radiation will normally ionize the air within the detector creating a current

• The alpha emitter is blocked when smoke enters the detector

• The alarm is triggered by a microchip when the sensor no longer detects alpha particles

Why is alpha particles used in smoke detectors

• alpha is the most weakly penetrating and strongest ionizer

• Beta and gamma have stronger penetrating power and weaker ionizing power

• If beta or gamma were used in this situation then they would pass straight through the smoke and the alarm wouldn’t go off

• Therefore since alpha is absorbed by smoke this makes it the most suitable for use

What is half life

This is the amount of time it takes for a number of nuclei of a sample of radioactive isotopes to decrease by half

What is contamination

The unwanted presence of materials containing radioactive atoms on other materials

What is the irradiation

This is the process of exposing a material to nuclear radiation the material does not become radioactive

Describe the nature of radioactive decay

• Random

• Which nuclei decays and when is only determined by chance

• It is impossible to determine what nuclei will decay and when

Compare irradiation and contamination

What is background radiation

this is radiation that exists around us all the time

What are the sources of background radiation

• natural

• Man made sources

What are the natural sources of radiation

• rocks

• Cosmic rays from space

• Foods

What are the man made sources of background radiation

• exposure from medical testing

• Fallout from nuclear weapons testing

What is becquerels

This measures the amount of radiation emitted by a source every second

What is counts per second

Measures the rate at which radiation hits a particular location

What is sieverts

This measures the received dose of radiation

What are the medical uses of radiation

• tracers: used to track the movement of substances- gamma

• Radiotherapy- gamma

• Sterilizing medical equipment- gamma

What are the risks of nuclear radiation

• kill or damage living cells

• Cause cancer

• Cause mutations

What is nuclear fusion

This is when two light nuclei join to form a heavier nucleus

What is nuclear fission

This is the splitting of a large unstable nucleus into two smaller nuclei

What is a chain reaction

During fission it produces two or three neutrons which move away at high speeds each of these neutrons can start another fission reaction which again creates excess neutrons

Why is nuclear fussion so hard to reproduce

This process requires extremely high temperatures

Why are high temperatures needed for nuclear fission

So two hydrogen nuclei have a repulsive force between them so high temperatures are required to give the nuclei enough energy to overcome the repulsive force

Describe the process of nuclear fission

neutron absorbed by a uranium nucleus nucleus splits into two parts and (2 / 3) neutrons (are released) and gamma rays (are emitted)

What is the advantage of radioactive waste have short half life

• activity decreases quickly

• Risk of harm decreases quickly