Nuclear Chemistry

Radioactive Decay

The last unit, we learned that all elements have different isotopes.

Example:1H (1 proton, 0 neutrons)2H (1 proton, 1 neutron)3H (1 proton, 2 neutrons)

Many isotopes are stablewill last forever

Some are not stable.

Radioactive Decay

Unstable isotopes are radioactive- able to emit particles or gamma rays

Radioactive (unstable) isotopes = radioisotopes

Radioisotopes decay into more stable forms.Radioisotopes release energy by emitting radiation

during the process of radioactive decay.

Radioactive Decay

Carbon-12 and carbon-13 are stableCarbon-14 is radioactive.

6 p+ and 6 n0 6 p+ and 7 n0 6 p+ and 8 n0

What makes a radioisotope unstable?

An isotope can be unstable if:it is too heavy (more than 83 protons).its neutron(n0) to proton(p+) ratio is too high.

its n0 to p+ ratio is too low.

Band of Stability

Types of RadiationAlpha radiation

Composition: Alpha particle (helium nucleus)

Symbol: α or HeCharge: +2Mass: 4 amuPenetrating power: Low (0.05 mm body tissue)Shielding: Paper, clothing

42

Alpha Decay

U23892

Th23490

He42

Nuclear equation:

U23892 He4

2+ Th234

90

Types of RadiationBeta radiation

Composition: Beta particle (electron)Symbol: β or eCharge: -1Mass: 1/1836 amuPenetrating Power: Moderate (4 mm body tissue)

Shielding: Metal foil

0-1

Beta Decay

C146

N147

e01-

C146

Nuclear equation:

e01-

+ N147

Types of RadiationGamma radiation

Composition: High-energy EM radiationSymbol: γ orCharge: 0Mass: 0Penetrating power: Very highShielding: Lead, concreteDecreases energy on nucleus

γ00

Tc9943 γ0

0 + Tc9943

RadioactivityRadioactive decay is known as natural

transmutation – the spontaneous nuclear decay of a radioisotope.

Occurs naturally – no outside influence needed

other types: artificial transmutation, fission, fusion

Hazards of Ionizing Radiation

Low level exposureRadiation danger is minimal.Cell damage, but cells recover and repairSeverely damaged cells self-destruct, limit damage

Non-lethal radiation exposure can still cause genetic mutation

If the mutation occurs in a gene that controls cell division, the cell could give rise to cancer.

Large radiation exposures can cause death much more quickly from severe tissue damage.

Uses of Radiation

Radioisotopic labelling – can be used to track the movement of a particular substance through a living organism.

Radiometric dating – used to determine the age of ancient objects.

Many uses in medicine, from imaging to cancer therapy.