Deck 10 = Radio Activity

Question 1

Atomic Theory?

Answer 1

• Geiger and Marsden fired alpha particles at a very thin gold film.

Question 2

Most alpha particles past through undetected - Conclusion?

Answer 2

Most of the atom is empty space.

Question 3

Some were deflected through small angles - Conclusion?

Answer 3

Nucleus is positively charged.

Question 4

Occasionally, an alpha particle would be deflected through a large angle. - Conclusion?

Answer 4

Tiny nucleus with a large mass, relative to alpha, so very dense.

Question 5

What did Bohr add to the Rutherford model?

Answer 5

The Bohr Model added the idea of electron shells of energy (energy level shells).

Question 6

Mass Number =

Answer 6

Protons + Neutrons

Question 7

What is a Isotope?

Answer 7

An atom with the same number of protons but a different number of neutrons.

Question 8

What is the difference between Rutherford’s model of the atom and Thomson’s plum pudding model?

Answer 8

The Rutherford model is made up of mostly empty space which the protons and neutrons are very small and dense in the middle. This is different to the ‘Plum Pudding’ as it just has a large sphere. The Rutherfod model also has orbiting electrons.

Question 9

What is a radioactive isotope?

Answer 9

“A radioisotope is an atom with a unstable nucleus.” Like an unstable building or cliff.

Question 10

Background Radiation is ………..

Answer 10

…….. everywhere, we are surrounded by it. Radioisotopes release particles when they fall apart.

Question 11

Sources of background radiation?

Answer 11

Radon Gasses in the ground. Also buildings and medical facilities and Food and Drink, cosmic rays.

Question 12

What is one thing we need to do when measuring the activity of a radioactive source?

Answer 12

We have to correct for background radiation. We can do this by first measuring for background radiation then subtracting this of the reading for the source.

Question 13

Total counts =

Answer 13

counts from radio isotope + background radiation.

Question 14

What is Ionising radiation?

Answer 14

When a radioisotope decays, ionising radiation may be released. These are dangerous because they can steel electrons from atoms. Which can lead to cancer. The three types are alpha, beta and gamma.

Question 15

Structure of Alpha Particle?

Answer 15

Each particle is 2 protons + 2 neutrons (identical to nucleus of helium - 4)

Question 16

Structure of Beta Particle?

Answer 16

Each particle is an electron (created when a nucleus decays)

Question 17

Structure of Gamma Rays?

Answer 17

electromagnetic waves similar to X-rays.

Question 18

Charge of alpha particles?

Answer 18

+2

Question 19

Charge of Beta Particles?

Answer 19

-1

Question 20

Charge of gamma rays?

Answer 20

0

Question 21

Mass of alpha particles?

Answer 21

high, 4amu

Question 22

Mass of beta particles?

Answer 22

low, weight of electron

Question 23

Mass of gamma rays?

Answer 23

-

Question 24

Speed of alpha partcle?

Answer 24

up to 0.1 x the spped of light.

Question 25

Speed of a beta particle?

Answer 25

up to 0.9 x the speed to light

Question 26

Speed of a gamma ray?

Answer 26

the speed of light.

Question 27

Ionising effect of alpha particle?

Answer 27

Strong

Question 28

Ionising effect of beta particle?

Answer 28

weak

Question 29

Ionising effect of gamma ray?

Answer 29

very weak

Question 30

Penetrating effect of Alpha Particle?

Answer 30

Not very penetrating, stopped by a thick peace of paper and skin, a few CM of air.

Question 31

Penetrating effect of Beta Particle?

Answer 31

Penetrating, but stopped by a few mm of metal.

Question 32

Penetrating effect of Gamma Ray?

Answer 32

very penetrating, never completely stopped, lead and thick concrete decreases intensity.

Question 33

Effects of fields on Alpha Particles?

Answer 33

deflected by magnetic and electric fields.

Question 34

Effects of fields on beta Particles?

Answer 34

Deflected by magnetic and electric fields?

Question 35

Effects of fields on Gamma Rays?

Answer 35

Not deflected by magnetic and electric fields.

Question 36

Name a radioactive isotope which occurs naturally in living things.

Answer 36

Carbon-12, 13-14

Question 37

What is the difference between the atoms of an isotope which is radioactive and the atoms of an isotope that is not?

Answer 37

The atoms in an isotope that is not radioactive will be neutral, radioactive isotopes also radiate radioactive materials.

Question 38

Example of Alpha emission?

Answer 38

Radium = Radon + alpha 226^88Ra = 222^86Rn + 4^2(ALPHA) - Mass number reduced by 4 - Atomic number reduced by 2

Question 39

Example of Beta Emission?

Answer 39

This is when a random neutron changes to a proton, emitting an electron. Iodine = Xenon + beta 131^53I = 131^54Xe + 0^-1(beta)

Question 40

Example of gamma Emission?

Answer 40

Atomic number remains the same.

Question 41

What is a Half Life?

Answer 41

The time it takes for half of the sample of a radioisotope nuclei to decay.

Question 42

Example of calculating half Life? A sample of a radioisotope has a mass of 250g. Calculate its mass after 64 minutes if it has a half life of 16 minutes.

Answer 42

64 minutes is 4 half lives. It is going to half every 16 minutes. It will 1/2 four times, 250g, 125g, 62.5g, 31.25g = 15.625g

Question 43

the bigger the radioisotope the .......

Answer 43

more stuff it will kick out.

Question 44

The activity of a radioisotope is measured in ..........

Answer 44

Becquerels Bq

Question 45

Mass left in sample is .......

Answer 45

proportional to activity (proportional = Jesus Fish)

Question 46

If samples of Strontium - 90 and radium - 226 both had the same activity, which would have the lower activity in 10 years time?

Answer 46

- strontium - 90

Question 47

If the activity of a sample of iodine -128 is 800 Bq, what would you expect the activity to be like after, 25 minutes - 50 minutes - 100 minutes -

Answer 47

400Bq 200Bq 50Bq

Question 48

What is nuclear fission?

Answer 48

The splitting of an atom which releases energy.

Question 49

Purpose of a moderator?

Answer 49

Graphite or water slows neutrons down so that they can successfully collide. to sustain reaction.

Question 50

Purpose of control rods?

Answer 50

Made or Boron, limit the rate of fisson by absorbing accsess neutrons.