Azra radioactive decay

RADIOACTIVE DECAYby : azyulail azra

radioactivity

• cannot be detected.

• energetic enough to knock electrons out of the atoms of a medium to produce ions.

• also known as ionising radiation.

The spontaneous disintegration of an unstable nucleus

particles

photons

emission of energetic

radioactive emissions

α-particleshelium nucleus

γ-rayselectromagnetic

waves

γ-raysβ-particlesα-particles

differencesCharge Positive

chargeNegative charge

No charge (neutral)

Speed Up to 10% of speed of light

Up to 99% of speed of light

Speed of light

Nuclide notation

-He42 e

0

-1

Penetratingpower

# Low# Stopped by a sheet of paper

# Average# Stopped by a fewmillimeters ofaluminium

# High# A few centimetersof lead can absorb a significantamount of it

γ-raysβ-particlesα-particles

Effect of magnetic field

Small deflection

Largedeflection in the opposite direction of the α-particles

Nodeflection

γ-raysβ-particlesα-particles

Effects of electric field

Small deflection towards negatively charged plate

Largedeflection towards positively charged plate

No deflection

γ-raysβ-particlesα-particles

Range in air

Several centimetres

Several metres

Several hundred metres

Tracks in cloud chamber

Straight and thick lines

Thin and wavy lines

Very fine short lines

Ionising power

Strong Medium Very weak

γ-raysβ-particlesα-particles

radioactive detectors

Cloud chamberGeiger-Muller TubeSpark counter

Photographic Film

cloud chamber

- to show the path of ionizing radiation.

- formed in the same way as the

condensation trails behind a high-flying aeroplane

α - particles β - particles γ - rays

photographic film- Found in badges worn by the staff at

radiation laboratories

GM tubeRadiation Enters through

mica window

Ionizes argon gas

Pulse of current

produced Pulse of current counted using

ratemeter/scaler

Number of counts

period of time

240 V

spark counter

radioactivesource is brought near

ionizes the air

between the gauze and the

wire

sparksare produced

Suitable for alpha rays

radioactive decay• Nuclei that have too few or too many neutrons are

most likely to be unstable.

• the process of a nucleus changing to a more stable nucleus while emitting radiation.

• Nucleus before the decay = parent nuclideproduct of the decay = daughter nuclide.

• The daughter nuclide may still be unstable and will eventually decay into another nuclide.

• This process continues until a stable nuclide is reached.

Alpha decay-This type of decay usually happens to the heavier unstable nuclei.

-The proton number is reduced by 2 while the nucleon number is

reduced by 4 and emit α-particles

U23892 He4

2Th +238 – 4 = 23492 – 2 = 90

Beta decay-Beta decay usually occurs for nuclei that have an

excess of neutrons.

- There is no change in the nucleon number but the

proton number increases by 1and emit β-particles

C14

6 e0-1N +14 - 0 = 14

6 - (-1) = 7

Gamma decay-occurs when an unstable nucleus releases its excess energy [ high

frequency electromagnetic waves ] called γ-rays.

-no change in proton number and

nucleon number but emit γ-rays-A nucleus that undergoes alpha or beta

decay may also emit γ-rays.

Co60

27 γCo +60

27

half-life

• Time taken for undecayed nuclei to be reduced to half of its original number

• The number of unstable nuclei have not decayed decreases with time.

• The half-life constant ~ the decay process is random and large.

Original number of

undecayed nuclei

Half of original number = 128

= 256It takes 3 hours for the undecayed nuclei to be reduced to half of original number.

∴ 1 half-life = 3 hours

64

128

Radionuclide Half-life (T1/2)90Sr Strontium-90 28.5 years

137Cs Caesium-137 30.1 years226Ra Radium-226 1600 years

14C Carbon-14 5736 years40K Potassium-40 1.28 x 108

years

Thank you !!!