Atomic Models
Radioactive Decay
Using Radioactivity
Nuclear Energy
Calculations
100
What is the approximate diameter of an atom?
1 x 10-10 m
100
What do we mean by "background radiation"?
Ionising radiation that is around us all the time, from a number of sources.
100
Give two dangers of using radioactive sources.
mutate DNA
mutate cells
kill cells
cause cancer
100
Give one disadvantage of using nuclear fuels to produce electricity.
Nuclear waste has to be disposed of.
Safety issues - if something goes wrong, it can go very wrong.
Public perception of danger
100
What is the half-life?
4 minutes
200
Who first proposed the idea of atoms having a nucleus?
Ernest Rutherford
200
What is the range of alpha particles in air?
A few cm
200
Give two safety precautions that a person who works with radioactive sources should take.
reduce exposure time
increase distance from the source
don't handle the source (use tongs)
work behind a screen
200
Give one advantage of using nuclear fuel instead of coal to produce electricity.
Nuclear fuel doesn't contribute to the greenhouse effect (No CO2 produced).
Much more energy produced (high energy density)
200
A scientist started with a mass of 60g of a radioactive substance.
After 30 days the mass was 7.5g. What is the half-life of the substance?
60 → 30 → 15 → 7.5
3 half-lifes
30 days ÷ 3 = 10 days
300
Draw a picture of a helium atom
300
How is a beta minus particle produced?
A neutron turns into a proton and emits a fast moving electron
300
Why are radioactive sources used as tracers in hospitals manufactured near to the hospital?
They have a short half-life, so need to be close, otherwise they would lose most of there radioactivity during transport.
300
What is the difference between nuclear fission and nuclear fusion?
Fission involves a large nucleus being split into 2 smaller nuclei.
Fusion joins together 2 smaller nuclei to make 1 large nucleus.
300
Complete this decay equation:
13153I → 0-1e + ?
13153I → 0-1e + 054Xe
400
Give the relative masses of:
a) proton
b) neutron
c) electron
a) 1
b) 1
c) 1/1835
400
What happens to the relative atomic mass and the atomic number when a nucleus undergoes alpha decay?
Mass number decrease by 4.
Atomic number decreases by 2.
400
Why is an alpha source used in a smoke alarm?
Alpha is very ionising, so will ionise air particles to complete the circuit in the smoke alarm
400
In a nuclear reactor, what is the role of the "moderator"?
It slows down neutrons, so they can be absorbed by the next atom
400
Polonium-208 undergoes alpha decay. Write a decay equation to show what is produced.
20884Po → 42He + 20482Pb
500
What do we mean by the term "isotope"?
An element that has the same number of protons, but a different number of neutrons
500
What happens to the relative atomic mass and the atomic number when a nucleus undergoes beta minus decay?
Mass number stays the same, atomic number increases by 1.
500
How are gamma rays produced in a PET scanner?
A positron is emitted from the source.
When it collides with an electron, both are annihilated.
Which produces 2 gamma rays, which travel in opposite directions
500
Why can nuclear fusion not happen at room temperature?
The nuclei do not have enough energy to overcome the electrostatic repulsion
500
Potassium-37 undergoes beta plus decay. Write a decay equation to show what is produced.
3719K → 0+1e + 3718Ar