Radiation and Radioactivity ▪ Know that radiation include all forms of wave and particle

energy ▪ Understand that radioactivity comes in two forms:

1. Waves: Consider the electromagnetic spectrum 2. Particles: alpha & beta

▪ Understand that radioactivity emanates from the nucleus of particular isotopes

Electromagnetic Spectrum of Radiation

▪ Be aware of the known types of radioactivity, particularly the first three:

1. Alpha particles: Helium nuclei – two protons & two neutrons

2. Beta particles: Electrons from the nucleus (?) 3. Gamma rays: electromagnetic radiation -waves 4. Proton Beam: H-1 atom 5. Neutron Beam: neutron 6. Positron: positive charged particle (not a proton)

Note: X-rays are NOT a form of radioactivity ▪ For electromagnetic radiation (non-particles), know the

wave-model and how waves are related to wavelength, frequency and energy

Proton

Electron

Neutron

Positron

Helium nucleus

Gamma ray

Particle or ray

Common nameof radiation Symbol Charge

Mass(amu)

Proton beam

Beta particle ()

Neutron beam

Alpha particle ()

Gamma ray

H

e or

n

e or +

He or

+1

-1

0

+1

+2

0

1

0.00055

1

0.00055

4

0

11

-10

01

+10

24

Positron emission

Writing Nuclear equations ▪ Understand the reason for radioactivity – unstable nucleus

caused by an imbalance of neutrons and protons ▪ Know how to write nuclear equations for

1. Beta emissions: o-1e particle is emitted therefore is on the right side of the arrow (must balance)

2. Alpha emissions: 42He particle is emitted therefore is on the right side of the arrow (must balance)

3. Gamma emission: γ ray is emitted therefore is on the right side of the arrow (no need to balance)

Beta Emission– Problem:Problem: carbon-14 is a beta emitter. When it

undergoes beta emission, into what element is it converted?

– Solution:Solution: it is converted into nitrogen-14

e-10

614 +?C

e-10

614 +N7

14C

Gamma Emission• In pure gamma emission, there is no change in

either the atomic number or the mass number of the element– a nucleus in a higher-energy state emits gamma radiation

as it returns to its ground state (its most stable energy state)

– in this example, the notation “11m” indicates that the nucleus of boron-11 is in a higher-energy (excited) state. In this nuclear decay, no transmutation takes place.

6

11m +B 611B

Alpha Emission• alpha emission:alpha emission: a type of nuclear decay in

which a helium nucleus is emitted from the nucleus– in alpha emission, the new element formed has an

atomic number two units lower and a mass number four units lower than the original nucleus.

24

92238 +Th90

234U He

24

84210 +Pb82

206Po +He

Know the penetrating power of nuclear radiation 1. Least: Alpha: most massive (He) and highly charged

(+2) 2. Mid: Beta: less massive (electron) and less charged (-1) 3. Most: Gamma (Wave) – no mass or charge

Half-life ▪ Define half-life ▪ Apply the concept of half-life to nuclear isotopes and Rx

1. Nuclear isotopes problems in OWL 2. Rx – See Half-life Power Point file in BB

Hydrogen-3 (tritium)Carbon-14Phosphorus-28Phosphorus-32Potassium-40Scandium-42Cobalt-60Strontium-90Technetium-99m

Indium-116

Iodine-131Mercury-197

Radon-205Radon-222Uranium-235

Name Half-life Radiation

12.26 y5730 y0.28 s14.3 d

1.28 x 109 y0.68 s5.2 y28.1 y6.0 h

14 s

8 d65 h

Polonium-210 138 d2.8 m3.8 d

4 x 109 y

BetaBetaPositronBetaBeta + gammaPositronGammaBetaGamma

Beta

Beta + gammaGammaAlphaAlphaAlphaAlpha