CP6 Radioactivity

Question 1

Explain why radiation can be damaging to humans

Answer 1

It is ionsing and can cause cancer

Question 2

What 2 pieces of equipment are used to measure and detect radioactivity?

Answer 2

Geiger counter/ GM tube and photographic film

Question 3

List ALL 6 sources of ionising radiation that you know

Answer 3

UV, X-ray, gamma, alpha, beta +, beta -,

Question 4

What is backround radiation?

Answer 4

The radiation that is always present in the world

Question 5

What causes there to be radiation in the world? (source of the backround radiation)

Answer 5

Humans setting off nuclear bombs, nuclear power stations melting down, nuclear waste, naturally occuring radioactive elements in the earth’s crust, radiation from space.

Question 6

What are the similarities and differences between isotopes?

Answer 6

Same number of protons but a different number of neutrons.

Question 7

What is the isotope notation for alpha, beta - beta +?

Answer 7

4 2 He
0 -1 B
0 +1 B

Question 8

What is the activity of a radioactive source?

Answer 8

The number of counts of radiation per second

Question 9

What is the S.I. unit for activity?

Answer 9

becquerel, Bq

Question 10

What safety precautions should someone who works with radioactivity undertake?

Answer 10

Keep a safe disstance, point source away from people, handle source with tongs, limit exposure time, use sheilding, use gloves, use mask, wear a film badge

Question 11

What equipment is used to measure radioactivity

Answer 11

Geiger counter

Question 12

Why does data in radioactivity experiments tend to be quite scattered?

Answer 12

Because radioactivity is a random process so there is variation in each reading

Question 13

What is the half-life of a radioactive compound? (2 definitions)

Answer 13

It is the time it takes for the count rate to half / the time it takes for half the nuclei to decay

Question 14

How do you find half-life from a graph?

Answer 14

Go down to half the value on the y axis and draw a line across to the curve. Draw a line down from there to the x-axis and read of the value of time that happened at.

Question 15

State the three subatomic particles

Answer 15

Protons, neutrons, electrons

Question 16

State the masses of the subatomic particles

Answer 16

Protons: 1, neutrons: 1, electrons: 0

Question 17

State the relative charges of the subatomic particles

Answer 17

Protons: +1, neutrons: 0, electrons: -1

Question 18

Why do atoms have no overall charge?

Answer 18

Because they have the same number of electrons as protons so the charges cancels each other out.

Question 19

What is the typical size of atoms or small molecules?

Answer 19

10^-10 m

Question 20

how small is the nucleus compared to the atom?

Answer 20

10 000 times smaller

Question 21

What happens to the electrons in an atoms when it absorbed electromagnetic radiation?

Answer 21

It moves to an orbit further from the nucleus

Question 22

What happens to the electrons in an atoms when it emits electromagnetic radiation?

Answer 22

the electron move to an orbit closer to the nucleus

Question 23

What is ionisation?

Answer 23

When at atom becomes an ion by losing electrons

Question 24

What is an alpha particle?

Answer 24

2 protons and 2 neutrons (a helium nucleus)

Question 25

what is a beta particle?

Answer 25

an electron emitted from the nucleus

Question 26

what is a gamma ray?

Answer 26

an electromagnetic wave

Question 27

List alpha, beta and gamma from most to least penetrating

Answer 27

Gamma, beta, alpha

Question 28

List alpha, beta and gamma from most to least ionising

Answer 28

Gamma, beta, alpha

Question 29

Describe the process of beta - decay

Answer 29

a neutron becomes a proton plus an electron which is emitted

Question 30

Describe the process of beta + decay

Answer 30

a proton becaomes a neutron plus a positron which is emitted

Question 31

Gamma radiation often occurs after another type of radiation. What is happening to the nucleus here?

Answer 31

The nucleus is rearranging

Question 32

What is the difference between contamination and irradiation?

Answer 32

In contamination a source of radiation has been eaten or touched which will continue to emit radiation and cause more damage. In irradiation radiation has hit and been absorbed causing damage but no further damage will be caused.

Question 33

What is the plum pudding model?

Answer 33

Atoms are spheres of positive charge with tiny negative electrons stuck in them

Question 34

Describe Rutherford's alpha particle scattering experiment

Answer 34

They fired a beam of alpha particles at a thin gold foil

Question 35

What were the results of Rutherford's alpha particle experiment?

Answer 35

Most of the alpha particles passed straight through, some were deflected by large amounts and some were deflected backwards

Question 36

How did Rutherford's alpha particle scattering experiment lead to the Bohr model of the atom?

Answer 36

In order for alpha partciles to be deflected backwards they must be hitting a very dense thing - the nucleus which contains most of the mass of the atom, for most alpha particles to pass through there must be lots of empty space. For alpha particles to be deflected they must be repelling the alpha particles and so the nucleus must be postively charged.