P2.5 What happens when radioactive substances decay, and the uses and dangers of their emmisions Flashcards
What is the basic structure of an atom?
A small central nucleus composed of protons and neutrons, surrounded by electrons
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
Very small
What is the relative charge of a proton?
+1
What is the relative charge of a neutron?
0
What is the relative charge of a electron?
-1
In an atom what is the number of electrons equal to?
The number of protons in the nucleus
What is the overall charge of an atom?
0
How do atoms become ions?
They may gain or lose electrons
What is an isotope?
When an atom has a different number of neutrons
Can you have different numbers of protons in an atom?
No it is always the same
What is the atomic number?
The number of protons (and therefore the number of electrons)
What is the mass number?
The total number of protons and neutrons
What do some substances give out from their nuclei all the time?
Radiation
What are substances that give out radiation from their nuclei?
Radioactive
What does background radiation come from?
Natural sources mainly: cosmic rays, rocks and soil, living things. However it can also come from artificial sources such as nuclear weapons and accidents
How many protons and neutrons does an alpha particle have?
2 protons and 2 neutrons
What is a beta particle?
An electron
What is gamma radiation?
A type of electromagnetic radiation
What happens in alpha decay?
The atomic mass number decreases by 4, and the atomic number decreases by 2
What is an example of an equation for alpha decay?
219 215 4
Rn ====> Po + α
86 84 2
What happens in beta decay?
The atomic mass number stays the same, but the atomic number increases by 1
What is an example of an equation for beta decay?
14 14 0
C ====> N + β
6 7 -1
What can alpha radiation be stopped / absorbed by?
A sheet of paper or a human hand
What can beta radiation be stopped / absorbed by?
A thin sheet of aluminium
What can gamma be stopped / absorbed by?
Lead or concrete
How far can alpha radiation travel in the air?
A few centimetres
How far can beta radiation travel in the air?
Tens of centimentres
How far can gamma radiation travel in the air?
Very large distances
What happens to alpha and beta at electric and magnetic fields?
They are deflected
Is gamma deflected at electric and magnetic fields?
No
Why are alpha and beta deflected by electric / magnetic fields when gamma is not?
Because alpha carries a positive charge and beta a negative charge, this means they are deflected by the magnetic / electric fields. Whereas gamma is neutral so does not carry a charge and is therefore not deflected
What is the half-life of a radioactive isotope?
The average time it takes for the number of nuclei of the isotope in a sample to halve. Or the time it takes for the count rate from a sample containing the isotope to fall to half its initial level
Why is alpha radiation so dangerous inside the body?
Because it is easily absorbed by cells
Why is beta and gamma radiation so dangerous outside the body?
Because they can penetrate the skin and damage the cells inside
Why are beta and gamma radiation less dangerous inside the body?
Because they are less likely to be absorbed by the cells, they will most likely just pass through them
Why is alpha radiation less dangerous outside the body?
Because it is less likely to penetrate the skin and reach the living cells inside the body
