TOPIC 7: RADIOACTIVITY

Question 1

What does an atom contain

Answer 1

protons, neutrons and electrons

Question 2

atomic number

Answer 2

the number of protons in the nucleus of an atom

Question 3

mass number

Answer 3

the number of protons and neutrons in the nucleus of an atom

Question 4

isotope

Answer 4

an atom of an element with the same number of protons but different number of neutrons

Question 5

nuclide

Answer 5

refers to a specific isotope of an element

Question 6

ionisation

Answer 6

the loss or gain of electrons

Question 7

cause of radiation

Answer 7

unstable nucleus (when it decays it emits radiation)

Question 8

What kind of process is radioactivity

Answer 8

a random process

Question 9

Causes of unstable nuclei

Answer 9

nucleus is too large, has too much energy or the number of protons is very different from the number of neutrons

Question 10

The different types of radiation/decay/emission

Answer 10

gamma, beta, alpha

Question 11

Alpha Emissions

Answer 11

• made up of 2 protons and 2 neutrons
• it is highly ionising because of its large size (+2)
• shortest range in air (travels only a few cm)
• it is blocked by everything

Question 12

Beta Emissions

Answer 12

• high energy electrons
• occurs when a neutron changes into a proton and an electron (positron)
• medium range in air
• blocked by aluminium

Question 13

Gamma Emissions

Answer 13

• electromagnetic waves
• have no charge (weakly ionising)
• highest energy of the different types of electromagnetic waves
• infinite range in air
• blocked by lead

Question 14

Ionising Radiation

Answer 14

an atom loses an electron due to radiation
- alpha are the most ionising form of radiation
- gammas are the least ionisation form of radiation

Question 15

nuclear fission

Answer 15

nuclear reaction in which a heavy nucleus splits int smaller nuclei and release energy

Question 16

nuclear fusion

Answer 16

nuclear reaction in which low atomic number atoms fuse to form a larger nucleus and release energy

Question 17

Origins of background count

Answer 17

food, cosmic rays, rocks, carbon-14

Question 18

half-life

Answer 18

The time taken for half the undecayed nuclei to decay or the activity of a source to decay by half

Question 19

deflection alpha

Answer 19

ELECTRIC: deflected by a small amount as it is charged and has mass

MAGNETIC: deflected since moving charges experience forces in a magnetic field

Question 20

deflection beta

Answer 20

ELECTRIC: deflected by a large amount as it is charged and has a small mass

MAGNETIC: deflected since moving charges experience forces in a magnetic field

Question 21

deflection gamma

Answer 21

there’s no charge, no deflection

Question 22

the effect of decay on alpha’s mass and atomic number

Answer 22

atomic number: decreases by 2
mass number: decreases by 4

Question 23

the effect of decay on gamma’s mass and atomic number

Answer 23

atomic number: doesn’t change
mass number: decreases by 1

Question 24

the effect of decay on beta’s mass and atomic number

Answer 24

atomic number: decreases or increase by 1
mass number: doesn’t change

Question 25

medical application of radiation

Answer 25

Medical procedures (ex: diagnosis and treatment of cancer
Sterilising food (irradiating food)
Sterilising medical equipment
Determining the age of ancient artefacts
Checking the thickness of materials
Smoke detectors (alarms)