Radiation

Question 0

The number of electrons in an atom is always the same as the number of protons, so atoms are electrically neutral overall. Atoms can lose or gain electrons. When they do, they form charged particles called ions:

1. ) if an atom looses one or more electrons, it becomes…
2. ) if an atom gains one or more electrons, it becomes…

Answer 0

1. ) a positively charged ion

2. ) a negatively charged ion

Question 1

What is the atomic number of an element?

Answer 1

Total number of protons

Question 2

What are isotopes?

Answer 2

Isotopes are the atoms of an element with different numbers of neutrons. They have the same proton number, but different mass numbers.

Question 3

When a radioactive isotope decays it….

Answer 3

Forms a different atom with a different number of protons

Question 4

What is the mass number?

Answer 4

The number of protons + the number of neutrons in an atom.

Question 5

Can you control radioactive decay?

Answer 5

No, it is a completely random process. Radioactive substances give out radiation from the nuclei of their atoms no matter what is done to them.

Question 6

Is radioactivity affected by physical conditions such as temperature or by any sort of chemical bonding?

Answer 6

No

Question 7

What three types of radiation are there?

Answer 7

Alpha, beta and gamma

Question 8

What is background radiation?

Answer 8

Radiation that is present at all times, all around us, everywhere we go.

Question 9

Where does background radiation come from?

Answer 9

1. ). Radioactivity of naturally occurring unstable isotopes which are all around us, in the air, in food, in building materials and rocks
2. ). Radiation from space, which is known as cosmic rays. These mostly come from the sun
3. ). Radiation due to man made sources e.g fallout from nuclear weapons tests and nuclear accidents.

Question 10

Alpha particles are…nuclei

Answer 10

Helium

Question 11

How many neutrons and protons does an alpha particle have?

Answer 11

2 neutrons and 2 protons- the same as a helium nucleus

Question 12

Why don’t alpha particles penetrate very far into materials and are stopped quickly, even when traveling through air?

Answer 12

Because they are relatively big, heavy and slow moving

Question 13

Why are alpha particles strongly ionising?

Answer 13

Because of their size they are strongly ionising, which just means that they bash into a lot of atoms and knock electrons off them before they slow down, which creates lots of ions.

Question 14

Beta particles are el……

Answer 14

Electrons

Question 15

Why are beta particles very small and fast?

Answer 15

Because they are electrons

Question 16

For every Beta particle emitted a neutron turns to a ….. in the nucleus

Answer 16

A neutron turns to a proton

Question 17

What charge does a Beta particle have?

Answer 17

-1

Question 18

Beta particles penetrate moderately
strongly
weakly

Answer 18

Beta particles penetrate moderately into materials before colliding

Question 19

Why are gamma rays weakly ionising?

Answer 19

Because they tend to pass through rather than collide with atoms. Eventually they hit something and do damage.

Question 20

What mass and charge are gamma rays?

Answer 20

Grammar rays have no mass or charge

Question 21

When traveling through a magnetic or electric field, both alpha and beta particles will be deflected. But in what direction?

Answer 21

They’re deflected in opposite directions because of their opposite charge

Question 22

Why are alpha particles deflected less in an electric or magnetic field compared to beta particles?

Answer 22

Alpha particles have a larger charge than beta particles, and feel a greater force in magnetic and electric fields. But they are deflected less because they have a much greater mass.

Question 23

Why do gamma particles not get deflected by electric or magnetic fields?

Answer 23

Because gamma radiation is an electromagnetic wave and has no charge, so it doesn’t get deflected.

Question 24

Why does the older a sample becomes, the less radiation is emitted

Answer 24

Because all the unstable nuclei disappear, the activity of decay decreases.

Question 25

Each time a decay happens and an alpha, beta or gamma is given out, it means……

Answer 25

One more radioactive nucleus has disappeared.

Question 26

What is the problem with measuring half life?

Answer 26

The activity never reaches 0

Question 27

What is half life?

Answer 27

The average time it takes for the number of uncle in a radioactive isotope sample to halve.

Question 28

The activity of a radioisotope is 640 cpm (counts per minute). Two hours later it has fallen to 80cpm. Find the half life of the sample,

Answer 28

Initial count: 640
Divided by 2
After one half life: 320
Divided by 2
After two half lives: 160
Divided by 2
After three half lives: 80

This calculation tells us that it takes three half lives for the activity to fall from 640 to 80. Hence the two hours represents three half lives, so the half life is 120 mins divided by 3= 40 minutes.

Question 29

How do you find the half life on a graph?

Answer 29

By finding the time interval on the bottom axis corresponding to a halving of the activity on the vertical axis.

Question 30

Smoke detectors use alpha radiation.

Answer 30

A weak source of alpha radiation is placed in the detector, close to two electrodes. The source causes ionisation, and a current flows between the electrodes. If there is a fire then smoke will absorb radiation, so the current stops and the alarm sounds.

Question 31

All isotopes which are taken into the body must be…

Answer 31

Gamma or beta. They should also have a short half life

Question 32

How can radiation be used to kill microbes?

Answer 32

Food can be exposed to a high dose of gamma rays which will kill all microbes, keeping the food fresh for longer.
Medical instruments can be sterilized in the same way.

Question 33

What uses of radiation are there?

Answer 33

Smoke detectors
Tracers in medicine
Radiotherapy 
X rays
Sterilization of food and surgical instruments.

Question 34

Radiation harms living cells

Answer 34

Alpha, beta and gamma radiation will happily enter living cells and collide with molecules. These collisions cause ionisation, which damages or destroys the molecules. This can give rise to mutant cells which divide uncontrollably. This is cancer. Higher doses tend to kill cells completely, which causes radiation sickness.

Question 35

The extent of the harmful side effects of radiation depend on:

Answer 35

How much exposure you have to the radiation

The energy and penetration of the radiation, since some types are more hazardous than others.