5.1 The nuclear atom

Question 1

source of evidence for the structure of the atom

Answer 1

alpha particle scattering

Question 2

radioactive decay

Answer 2

the random process of the nucleus of an unstable isotope giving out radiation to make it stable

Question 3

activity

Answer 3

the rate of which an unstable nuclei decay

Question 4

unit of activity

Answer 4

becquerel (Bq)

1 Bq = 1 decay per second

Question 5

measuring device of activity

Answer 5

geiger-muller tube

Question 6

count rate

Answer 6

number if decays recorded each second by a detector, like a geiger-muller tube

Question 7

nuclear energy

Answer 7

energy released in a nuclear reaction

Question 8

nuclear reactions

Answer 8

• nucleus in involved- not the usual electrons

- the products are completely different atoms than the reactants

Question 9

unit of measuring mass of an atom

Answer 9

atomic mass unit (amu)

1 amu = 1.66x10-27 kg

Question 10

unit of nuclear energy

Answer 10

mega electron volt (MeV)

1 MeV = 1.6x10-13 J

Question 11

background radiation

Answer 11

the radiation that is always around us in the environment

Question 12

types of radiation

Answer 12

• alpha particles
• beta particles
• gamma rays

Question 13

alpha particles

Answer 13

• 2 protons and 2 neutrons

- emitted from too large nuclei

Question 14

beta particles

Answer 14

• electron ejected from nucleus at very high speed

- emitted from nuclei with too many neutrons

Question 15

gamma rays

Answer 15

• electromagnetic ray

- no charge

Question 16

properties of alpha particles

Answer 16

• most ionising
• large; shortest traveler in air (5 cm)
• stopped by a sheet of paper`

Question 17

properties of beta particles

Answer 17

• moderately ionising
• travel 15 cm in air
• stopped by a few mm of aluminum

Question 18

properties of gamma rays

Answer 18

• least ionising
• travels several metres
• stopped by several cms of lead

Question 19

alpha decay

Answer 19

• atomic number decreases by 2

- mass number decreases by 4

Question 20

beta decay

Answer 20

• atomic number increases by 1

- mass number stays the same

Question 21

gamma decay

Answer 21

no change in mass or atomic number

Question 22

half-life

Answer 22

the time it takes for the number of nuclei of the radioactive isotope in a sample to halve (decay)

Question 23

tracers

Answer 23

radioactive isotopes that can be added to some fluid so that the flow of that fluid can be monitored

Question 24

uses of tracers

Answer 24

medicine- added to blood to check blood flow and search for blockages
industry- added into an oil pipeline in order to check for any leaks

Question 25

radiotherapy

Answer 25

treatment of cancer using radiation

Chemotherapy is treatment using chemicals

Question 26

dangers of ionisation (radiation)

Answer 26

cause chemical changes resulting in

• mutations
• cells becomes cancerous
• kills the cell

Question 27

safety precautions when handling radioactive sources

Answer 27

• store source in lead lined box away from people
• minimise amount of time handling them
• stay as far as possible, use togs when handling at arm length distance

Question 28

products of nuclear fission

Answer 28

2 daughter nuclei, 2-3 neutrons, gamma rays, kinetic energy

Question 29

what happens to the nuetrons produced

Answer 29

they trigger more isotopes and so on whoop (chain reaction)

Question 30

controlled fission chain reaction

Answer 30

release energy in nuclear reactor

Question 31

uncontrolled fission chain reaction

Answer 31

explosion in a nuclear weapon

Question 32

nuclear fusion

Answer 32

• two light nuclei join to form heavier nucleus

- some of the mass of the nuclei can then be converted into energy released as radiation

Question 33

where is nuclear fusion seen

Answer 33

it is the process that releases energy in stars like the son