P4 Atomic Structure Flashcards
Give an approximation for the radius of an atom
1x10^-10 metres
What are the three subatomic constituents of an atom?
Proton
Neutron
Electron
Where is the most of the mass of an atom concentrated?
In the nucleus
Approximately what proportion of the total radius of an atom is the radius of the nucleus?
1/10,000
Describe the arrangement of protons, neutrons and electrons in an atom
The protons and neutrons are found in the atoms nucleus
The electrons are found in discrete energy levels around the nucleus
What type of charge does the nucleus of an atom have? Why?
Positive charge
The nucleus contains protons and neutrons
Protons have a positive charge
Neutrons have no charge
Give two ways that an atoms electron arrangement can be changed
Absorbing electromagnetic radiation
Emitting electromagnetic radiation
Explain how an atoms electron arrangement changes when it absorbs electromagnetic radiation
Electrons move further away from the nucleus
They move to a higher energy level
Explain how an atoms electron arrangement changes when it emits electromagnetic radiation
Electrons move closer to the nucleus
The move to a lower energy level
What are the three types of radiation?
Alpha
Beta
Gamma
What is the charge of alpha radiation
2+
What is the charge of beta radiation
1-
What is the charge of gamma radiation
No charge
What is radiation
Radiation is either particles or waves emitted by an unstable nucleus which carry energy away from the nucleus to make it more stable
What has the most penetrating power?
Gamma
Lead stops it
What is the most ionising
Alpha particles are the most ionising as they have the greatest charge
What is the least ionising
Gamma radiation is the least ionising because it has no charge
Define ionising
Ability for an atom to lose an electron
What is background radiation
Background radiation is ionising radiation from radioactive sources in the environment
What is an example of natural source background radiation
Rocks
Food
Cosmic rays
What are examples of man made background radiation
Medical sources
Nuclear power plant
What is the plum pudding model
Solid ball of positive charge
It contained negative electrons within the positive solid
What is the change in the nucleus of alpha decay
Loses two protons and two neutrons
What is the change in the nucleus of beta decay
Neutron goes to proton then electron is emitted
What is half life
The half life is the time taken for the number of radioactive nuclei in an isotope to half. This can take hours, weeks, years
What is the half life equation
Count rate (number of unstable nuclei after n half lives) = initial count rate (number of unstable nuclei)/ ——————————————————
2^n
Define irradiation
Irradiation is when a surface is exposed to radiation. An example is X-rays, sterilising fruit
Define contamination
Contamination is when an object is mixed with a radioactive substance. An example is water pipe leaks
