Radioactivity

Question 1

Radioactivity

Answer 1

Spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation

Question 2

Radioisotopes

Answer 2

Radioactive isotope

Question 3

Half life of an element

Answer 3

Time taken for half the nuclei in any given sample to decay

Question 4

Henri Becquerel

Answer 4

• Studying effects of light on uranium salts

- Found uranium salt was giving off some type of radiation

Question 5

Alpha radiation - Nature

Answer 5

Helium nuclei (2 protons + 2 neutrons)

Question 6

Alpha radiation - Charge

Answer 6

+

Question 7

Alpha radiation - Penetrating power

Answer 7

Stopped by paper

Question 8

Alpha radiation - Use/example

Answer 8

Americium-241 used in smoke detectors

Question 9

Beta radiation - Nature

Answer 9

Electrons

Question 10

Beta radiation - Charge

Answer 10

-

Question 11

Beta radiation - Penetrating power

Answer 11

Stopped by aluminium 5mm thick

Question 12

Beta radiation - Use/example

Answer 12

Carbon-14 used to date organic material

Question 13

Gamma radiation - Nature

Answer 13

Waves of high energy

Question 14

Gamma radiation - Charge

Answer 14

None

Question 15

Gamma radiation - Penetrating power

Answer 15

Stopped by several cm of lead

Question 16

Gamma radiation - Use/example

Answer 16

Cobalt-60 used in cancer treatment

Question 17

Used to detect radiation

Answer 17

Geiger-Muller Tube

Question 18

Chemical reactions

Answer 18

• Involved electrons rather than nucleus
• Elements unchanged/(No new element formed)
• No release of nuclear radiation
• Chemical bonds broken + formed

Question 19

Nuclear reactions

Answer 19

• Changes take place in nucleus
• New element formed
• Nuclear radiation released
• No bond breaking or formation

(when writing this, try not to use nuclear radiation and change in nucleus as the two answers, use one of them and then use a diff one from this list)

Question 20

Henri Becquerel

Answer 20

• Exposed uranium salts + photographic plates in sunlight - thought energy from sun being released by crystals created image on the plates
• left in a closed drawer w/ plates, same image formed, no sunlight present

Question 21

Marie Curie

Answer 21

• Marie + Pierre Curie continued Becquerel’s work,
• Experimenting pitchblende, realised there must be elements more radioactive than uranium
• Named + discovered polonium + radium

Question 22

Marie Curie nobel prizes

Answer 22

• 1903 - Becquerel & Curie & Curie - discovery + research into radioactivity
• 1911 - Discovery of radium + polonium, + isolation of radium

Question 23

equations for loss of alpha particle and beta particle

Answer 23

in hardback

Question 24

what changes take place in structure of nuceus of an atom when beta decay occurs?

Answer 24

a neutron changes into a proton and an electron is emitted from nucleus

Question 25

carbon-14 has a half-life of 5730 years

A fragment of yew contained 1.5 x 10¹² carbon-14 atoms. Explain why it must have contained 3.0 x 10¹² carbon-14 atoms 5730 years before the analysis

Answer 25

5730 is the half-life (number of carbon-14 atoms halved in 5730 years)

Question 26

what mass of carbon-14 did the fragment contain 5730 years before the analysis?

(contained 3.0 x 10¹² carbon-14 atoms 5730 years before the analysis)

Answer 26

3. 0x10¹² / 6.0 x 10²³ = 5.0 x 10⁻¹² moles of carbon-14 originally
4. 0 x 10 ⁻¹² x 14 = 7.0 x 10⁻¹¹ originally

(turn to moles first using avogadro’s number. Then, use n = m/mr formula to find mass. Make sure to multiply by 14 here as Mr instead of 12 which is on log table as it specifies that it is carbon-14!!!)

Question 27

pay attention when doing calculations

Answer 27

pay attention to whether they want the answer in atoms or molecules, and whether they give you info in atoms/molecules…

Question 28

properties of beta particles

Answer 28

• negative charge
• negligible mass (mass of electron)
• stopped by aluminium 5mm thick
• moderately ionising

Question 29

caesium-137 has half-life of 30 days, what fraction of this mass remained after 90 days?

Answer 29

1/8

1/2 x 1/2 x 1/2

Question 30

explain why the carbon-12 to carbon-14 isotope ration in something changed over 5500 years

Answer 30

carbon-14 decayed (changed to nitrogen)

Question 31

risk associated with exposure to alpha radiation

Answer 31

causes ionisation / causes cancer

Question 32

why are occupants of a house with smoke detectors containing americium-241 not at risk from alpha radiation?

Answer 32

radiation is not very penetrating

Question 33

half life of amiericium-241 is 432 years

does it need to be replaced regularly in smoke detectors?

Answer 33

half life is over 400 years, sample does not deplete quickly

Question 34

properties of alpha particles

Answer 34

• positive charge
• poor penetration (stopped by sheet of paper)
• strong ionisation

Question 35

ionisation order of radiations

Answer 35

know from notes

Question 36

explain how the carbon-14 idotope allows certain archaeological discoveries to be dated

Answer 36

in living things, the ratio of carbon-12 to carbon-14 is constant

after death, carbon-14 decays and the changed ratio and half-life used to find age

Question 37

order of penetrating power of radiations

Answer 37

alpha
beta
gamma

Question 38

changes when alpha decay occurs

Answer 38

During alpha decay, an atom’s nucleus sheds two protons and two neutrons