Radioactivity

Question 1

atomic number

Answer 1

number of protons

Question 2

mass number

Answer 2

number of protons and neutrons

Question 3

Adding or removing electrons

Answer 3

Ionisation

Question 4

Isotopes

Answer 4

equal number of protons but different number of neutrons

Question 5

Isotopes

Answer 5

equal number of protons but different number of neutrons

Question 6

1 Becquerel (1 Bq)

Answer 6

an emission fo 1 particle/second

Question 7

Alpha Particles

Answer 7

helium nucleus 4 over 2 HE

5 cm

stopped by paper

nucleus transforms into another nucleus with -4 to the mass number and -2 to the atomic number

Question 8

Beta particles

Answer 8

Ejected from nucleus when neutron turns into proton and electron

Fast moving electrons 0 over -1 e

many metres

stopped by aluminium sheet mm thick

nucleus transforms into another nucleus with 0 to the mass number and 1 to the atomic number

Question 9

Gamma ray

Answer 9

A short -wavelength electromagnetic wave

great distances

can only be absorbed by thick lead sheets, cm

no mass or charge

Question 10

Neutron decay

Answer 10

neutron is lost

nucleus transforms into another nucleus with -1 to the mass number and 0 to the atomic number

Question 11

Radioactive decay

Answer 11

Random process

half life-

1 half life - 1/2 left

2 half life - 1/4 left

3 half life - 1/8 left

etc

Question 12

Background radiation

Answer 12

Low amounts of radiation all around -not serious health risk

come from rocks

sun and outer space - cosmic rays

radon gas

Question 13

Hazards of radiation

Answer 13

ionising radiations

alpha destroys body tissue - most dangerous

Question 14

Radiation dose measurement

Answer 14

sieverts, Sv

Question 15

Nuclear fission

Answer 15

The splitting of a large atomic nucleus into two smaller nuclei.

Controlled in a nuclear reactor by boron rods

Can be triggered by a neutron. Triggers other reactions - chain reaction

Question 16

Nuclear energy

Answer 16

Produced in nuclear fission.

kinetic energy - thermal energy

Question 17

Moderator purpose

Answer 17

To slow down neutrons that are produced in fission. Nucleus split more easily if neutron is slower

Question 18

Fuel rods

Answer 18

Made from uranium-238 enriched with 3% uranium-235

Embedded in graphite - moderator

Question 19

Boron rods

Answer 19

regulate the rate of the production of energy

Absorb neutrons - slows down reaction

Question 20

Concrete shielding

Answer 20

vital protection for workers

Contains a lot of water. No neutrons through.

Question 21

Nuclear fusion

Answer 21

Two small nuclei combine or fuse to form a single larger nucleus

Form a 4,2 He nucleus and a neutron is ejected

Gamma ray produced- carries away energy

requires a lot of heat energy to overcome electrostatic repulsion.

Source of energy in stars

Question 22

Uses of Radioactivity

Answer 22

Medicine - Thyroid gland - radioactive iodine is absorbed

            - Most medical equipment is exposed to intense gamma radiation - kills bacteria
           - Treatment of cancers - radiation to kill cancer cells.

Industry - radioactive tracers detect leaks - fed into pipe and gm tube detects an increase in radiation levels.

Irradiation and contamination