Radioactivity

Question 1

what is meant by proton number?

Answer 1

The proton number is the is the number at the bottom of an element, it tells us how many protons and electrons that element has

Question 2

What is meant by nucleon number?

Answer 2

The nucleon number is the number at the top of an element, it tells us how many protons and neutrons the element has

Question 3

What is half life?

Answer 3

Half life is the time taken for the number of radioactive nuclei/mass activity to reduce to half of its initial value

Question 4

How is half life calculated?

Answer 4

At the beginning (time 0), the counts per minute was 80. To find the half life we need to look on the graph at which time the count rate was 40 counts per minute (half).
This is the half life of the substance. In the above example the half life is 2 days.
From the half life you can find out how much of a substance will remain after a period of time.

Question 5

What is meant by an isotope?

Answer 5

An isotope of an element is where an atom has the same number of protons but
different numbers of neutrons in its nucleus.

Question 6

Why are certain nuclei are radioactive?

Answer 6

When a nucleus has an imbalance between the number of neutrons and protons it
may be unstable. If this is the case then we class this atom as Radioactive and
it will give off radioactive emissions. When a nucleus gives off radiation we call
this radioactive decay. However, we cannot predict when any particular nucleus
will decay as it’s a random process

Question 7

What are alpha emissions?

Answer 7

Alpha radiation is made of 2 protons + 2
neutrons
(helium nuclei). Very heavy (relatively).
Positive charge (+2)
VERY ionising (most dangerous!)
Not very penetrative (stopped by thin
layer of air/paper/skin)

Question 8

What are beta emisssions?

Answer 8

Beta radiation are electronsemitted from
the nucleus..
Negative charge (-1)
Stopped by Aluminium

Question 9

What are gamma emissions?

Answer 9

An electromagnetic wave (from EM
Spectrum)
Very penetrative – reduced by lead
Has no mass
Least ionising

Question 10

What radiation cant penetrate a sheet of paper?

Answer 10

Alpha Radiation

Question 11

What radiation cant penetrate an aluminium sheet?

Answer 11

Alpha Radiation and Beta radiation

Question 12

What is background radiation?

Answer 12

If you were to get a Geiger Counter and put it far away from any radioactive materials, it would still detect radiation as there is always a low level of ioising radiation all around us. This is called background radiation

Question 13

What causes background radiation?

Answer 13

Radon gas, Cosmic Ray’s, and Food and drink are all natural causes of background radiation. Some man made sources are medical devices (x rays) and nuclear energy.

Question 14

What are the problems assosiated with radon gas?

Answer 14

High levels of radon gas can cause lung cancer as the gas is breathed into the lungs.
Radon gas is an alpha emitter.
Alpha is the most ionising form of radiation and will do the most damage when inside your body.

Question 15

How is radon gas build up prevented?

Answer 15

Radon gas enters through gaps and cracks in the floor. To reduce radon levels in our homes we can:
1. Improve ventilation by opening
windows.
2. Fit airbricks to improve
underfloor ventilation.
3. Install a fan to extract radon gas
from a sump underneath the house

Question 16

Why are radioactive isotopes difficult to dispose of?

Answer 16

only time can reduce the radiation
emitted from a radioactive material and some materials remain radioactive for thousands of years (have long half lives). It is very costly to process, store and guard nuclear waste.

Question 17

What is meant by nuclear fission?

Answer 17

Nuclear fission is when a neutron is fired into a uranium atom nucleus, this causes the uranium atom to split. After the uranium atom is split the energy created causes a chain reaction making more and more uranium atoms split. When the uranium atom splits it gives off immense amounts of energy which is what nuclear power stations use. Nuclear fission however does create radioactive waste that is very hard to get rid of.

Question 18

Describe how a nuclear reactor works (Fuel Rods, Boron Control Rods, Graphite Moderator)

Answer 18

Fuel rods contain the Uranium which undergoes fission to produce heat energy. This heat energy is used form steam which turns turbines connected to generators.
Large numbers of neutrons are produced during fission and if all of these neutrons were allowed to go on to split Uranium nuclei, too much energy would be produced resulting in a meltdown or explosion e.g. Chernobyl (due to an uncontrolled chain reaction). Control rods absorb excess neutrons when lowered into the reactor. Uranium atoms will only ‘capture’ neutrons and split if the neutrons move towards them at a certain speed. The graphite moderator slows down fast moving neutrons to allow them to be ‘captured’ by Uranium. Modern reactors may use water as both moderator and coolant (older reactors use CO2 as a coolant).

Question 19

What is meant by nuclear fusion?

Answer 19

Nuclear fussion is the process of forcing two nuclie to collide. usually this only happens in stars due to the intense conditions neccassary however we have managed to achieve this on earth. Deuterium and tritium are the two helium isotopes used in nuclear fussion

Question 20

Why is nuclear fussion difficult to achieve on Earth?

Answer 20

Nuclear fussion requires intense conditions for it to occur, the nuclie must be above 100 million degrees celcius and under intense pressure