Nuclear Chemistry

What is a Nuclear Decay?When the nucleus of an atom breaks down

to form a different element

How do nuclear and chemical reactions differ?

Nuclear reactions involve the nucleus (protons and neutrons)

BUTchemical reactions involve the

transfer and sharing of electrons

Ionizing Radiation:

Nuclear decay is a form of Ionizing Radiation: High energy that ejects electrons and transforms

molecules into reactive unstable fragments Includes parts of the electromagnetic spectrum:

UV, X-ray, Gamma Ray

Radiation is organized on the Electromagnetic Spectrum

LOW ENERGY

HIGH ENERGY

V I B G Y O R

Band of Stability

After element 83 (Bismuth)the elements are naturally unstable

and may emit decay particles

The bigger the atom gets and the further from a 1:1 ratio of

protons and neutrons, the less stable the

atom is

Types of Radioactive Decay

Decay Type Symbol Comp

ositionNuclear Symbol Strength Penetratin

g PowerAlphaBeta

Gamma

Radioactive Decay

Steps to writing decay reactions:

1. Write the nuclear symbol for the element that is given.

2. Draw an arrow.3. Identify the type of particle that has decayed

and write it after the arrow.4. Balance the mass number (top) and the

atomic number (bottom). 5. Identify the new element.

Nuclear Symbols Review

• The superscript indicates the mass number and the subscript indicates the atomic number.

C12

6

XAZ

Mass Number

Atomic NumberElement Symbol

Alpha Decay Loss of an alpha particle

42He

239Pu 94

235U 92

Beta Decay Loss of a beta particle

0-1 e

42K 19

Gamma Decay Loss of a gamma particle

Alpha and gamma decay of:

00γ

239Pu 94

Half Life

Half-LifeTime required for half a sample to decay

The stability of the isotope is what determines the rate of decay.

Less Stable = Faster Decay

Half-Life After each half-life, half of

the sample decays. Start = 100%

40 blue particles are present 1 half-life = 50%

20 blue remain 2 half-lives = 25%

10 blue remain 3 half-lives = 12.5%

5 blue remain 4 half-lives = 6.25%

2.5 blue remain

Amount never becomes zero!!

Half-Life After 10 half-lives sample considered

nonradioactive because it approaches the level of background radiation.

Because the amount never reaches zero, radioactive waste disposal and storage causes problems. Would you want radioactive waste stored in your community?

How can we get rid of nuclear radioactive waste?

Half Life PracticeExample 1:

The half-life of mercury-195 is 31 hours. If you start with a sample of 5.00 g, how much of it will still be left after 93 hours?

Half Life Practice ContExample 2:

How many half lives have passed if there is only 1.875 g left of a 30 g sample?

If the half life for this sample is 1 hour, how many total hours have gone by?

Applications

Where do we use nuclear chemistry?

Nuclear reactions power the sunNuclear power plants provide electricityMedical uses:

x-rays, cancer treatment, radioactive tracers Industrial uses:

Sterilize equipment, sterilize (irradiate) food, x-rays of metal equipment (scan for cracks in airplanes)

Military

FusionTwo light atoms combine to form a heavier

atom of higher energy

This reaction powers the sun!

FissionOne heavy atom breaks down into two or more

smaller atoms and produces energyThis becomes a chain reaction

(as one atom splits and hits more, and those split and hit more)

Supercritical:creates a great release of energy - atomic bomb

Ping Pong Video

Controlled FissionControlled Fission: used for nuclear power

Controlled Diagram:Control Rods to

limit nuclear fission!

Fission heats the water that turns to steam and moves the

turbines