Radioactivity

Question 1

define isotope

Answer 1

atoms of the same element- have the same number of protons but different numbers of neutrons

Question 2

how does ionisation occur

Answer 2

gain or loss of electrons

Question 3

what is radioactive decay

Answer 3

as some isotopes are unstable they try and emit particles from the nucleus to stabilise
decay is random and spontaneous

Question 4

3 types of ionising radiation

Answer 4

alpha, beta, gamma

Question 5

what is an alpha particle

Answer 5

2 protons and neutrons - He nucleus

Question 6

what happens when a nucleus emits an alpha particle

Answer 6

Ar falls by 4, atomic number falls by 2

Question 7

what is a beta particle

Answer 7

emission of an electron

changes a neutron into a proton

Question 8

what happens when a nucleus emits a beta particle

Answer 8

Ar has no change

atomic number increases by 1

Question 9

what is gamma radiation

Answer 9

an atom decays by emitting a gamma ray

Question 10

what happens when a nucleus emits gamma radiation

Answer 10

releases energy- no change to Ar or atomic no

Question 11

relative penetrating abilities of alpha, beta and gamma

Answer 11

alpha- lowest, blocked by skin/ paper, cannot travel far
beta- moderate, blocked by thin aluminium foil
gamma- highest, blocked by thick lead walls

Question 12

relative ionising abilities of alpha, beta and gamma

Answer 12

alpha= least
beta= moderate
gamma - most

Question 13

dangers of ionising radiation

Answer 13

irradiation- exposure to the source but not in contact. therefore if object is moved away from source, damage is stopped

Question 14

uses of ionising radiation

Answer 14

treating cancer (radiotherapy)
sterilising medical equipment
detecting tumours

Question 15

activity of radioactive sources

Answer 15

the rate at which a source of unstable nuclei decays measured in decays per second. The unit for activity is the Becquerel (Bq)

Question 16

half life

Answer 16

measures the time it takes for a given amount of the substance to become reduced by half as a consequence of decay

Question 17

what does 1 Bq mean

Answer 17

1 Bq = 1 decay per second.

Question 18

nuclear fission

Answer 18

when heavy weight nuclei split to form smaller weight nuclei
caused by the absorption of neutrons

Question 19

how does fission cause chain reactions

Answer 19

neutrons released from one reaction collide w/ other atoms causing fission to occur

Question 20

give an example heavy atom used in fission

Answer 20

Uranium 235

fission produces Barium and krypton

Question 21

nuclear fusion

Answer 21

when 2 lightweight nuclei fuse to form 1 heavy weight nucleus
releases energy

Question 22

fusion of H to form He

Answer 22

1) 2H+ fuse to form to from hydrogen 2 isotope, positron and neutrino
2) H+ and hydrogen fuse to form helium 3 isotope, gamma ray and energy
3) 2 helium-3 isotopes fuse to form helium and 2 hydrogen nuclei

Question 23

why does fusion need high temperatures

Answer 23

to overcome the electrostatic repulsion of positive nuclei

Question 24

potential use of fusion

Answer 24

would act as a renewable energy source, infinite resource

Question 25

state which isotopes are formed from the fission of Uranium 235

Answer 25

Barium 141

Krypton 92