Decay

Question 1

Radioactive decay

Answer 1

If an element is unstable, the nucleus can undergo random radioactive decay

Question 2

Alpha (a) decay

Answer 2

-an alpha particle is a helium nucleus
-when emitted, mass number decreases by 4, atomic number decreases by 2

Question 3

Beta minus (B-) decay

Answer 3

-a beta minus particle is a fast moving electron emitted from the nucleus
-when emitted, mass number stays the same, atomic number increases by 1
- when a neutron decays to become a proton and an electron

Question 4

Beta plus (B+) decay

Answer 4

-a beta plus particle is a fast moving positron emitted from the nucleus
-when emitted, mass number stays the same, atomic number decreases by 1
- when a proton decays to a neutron and a positron

Question 5

Gamma (y) decay

Answer 5

-gamma rays are short wavelength, high frequency EM waves
-when a nucleus is excited, it emits a gamma ray, mass and atomic number don’t change

Question 6

Neutron decay

Answer 6

-emission of a neutron from a nucleus
-mass number decreases by 1, atomic number stays the same

Question 7

Properties of a, B, y

Answer 7

a - strongly ionising, short range
B - less strongly ionising, medium range
y - weakly ionising, long range

Question 8

Half life

Answer 8

Time it takes for number of nuclei in a sample to half (Bq)
1Bq = 1 decay per second
Eg.
Half life of something is 30 years, initial activity is 40kBq, calculate Bq after 90 years

3 half lives 20, 10, 5 = 5kBq

Question 9

Irradiation

Answer 9

Process of exposing an object to ionising radiation

Question 10

Radioactive contamination

Answer 10

Contains radioactive nuclei which will go on to decay and release ionising radiation

Question 11

Uses of radiation

Answer 11

-sterilisation of food and medical equipment (gamma rays)
-radioactive tracers
-PET scans
-carbon dating
-smoke detectors

Question 12

Radiotherapy

Answer 12

Internal - beta particles deposit energy, killing the overactive thyroid cells
External - energy gamma rays carry kills cancer cells

Question 13

Carbon dating

Answer 13

By measuring the amount of carbon 14 in a once living material, we can estimate its age

Question 14

Smoke detectors

Answer 14

1) alpha particles produced ionise air inside detector
2) these charged particles complete the circuit inside the smoke detector
3) when smoke enters, the ionisation inside decreases, causing the current to decrease, starting the alarm