• What do the following terms mean?• Radiation• Radioactivity• Fusion • Fission

S-79Students will distinguish the characteristics and components of radioactivity.

SPS3 Students will distinguish the characteristics and components of radioactivity.a. Differentiate among alpha and beta particles and gamma radiation.b. Differentiate between fission and fusion.c. Explain the process of half-life as related to radioactive decay.d. Describe nuclear energy, its practical application as an alternative energy source,

and its potential problems

Chapter 10

Nuclear Chemistry

What happens during nuclear decay?

What are three types of nuclear radiation?

How does nuclear radiation affect people?

10.1 Radioactivity

• Antoine Henri Becquerel – French physicist– Accidentally discovers that Uranium left

next to photographic plates will cause them to become cloudy

– Uranium must be emitting some ray that exposed the film

– Radioactivity – an unstable atom emits particles and energy

10.1 RadioactivityWhat happens during nuclear decay?

• Radioisotope – any atom that has an unstable nucleus (radioactive isotope)– Written with the name of the element

and the mass number (total of protons and neutrons)

– Uranium-238

10.1 RadioactivityWhat happens during nuclear decay?

• Nuclear Decay – atoms of one element change into atoms of another element– Uranium 238 decays to become thorium

234

• Three common types of Nuclear Radiation– Alpha Decay– Beta Decay– Gamma Ray

10.1 RadioactivityWhat happens during nuclear decay?

• Alpha Particle - – Made of two protons and two neutrons– Postively charge– A Helium nucleus– The equation for the Alpha Decay of

Uranium-238 to Thorium-234 would be written as

– Can be stopped by a sheet of paper

10.1 RadioactivityWhat are three types of nuclear radiation?

• Beta Particle - – Electron emitted from the nucleus (not from

the electron cloud)– Negative charge– A neutron decays to a proton and an

electron– Described by the equation

– Mass stays the same, protons increase by 1– Can be stopped by a thin sheet of metal

10.1 RadioactivityWhat happens during nuclear decay?

• Gamma Ray - – Electromagnetic ray emitted by decay– No charge, no mass, no change in

nucleus– Energy of the nucleus decreases– Stopped by 5 cm of lead, or 2 m of

concrete

10.1 RadioactivityWhat happens during nuclear decay?

• Background Radiation – occurs naturally in the environment– Cosmic rays– Radioisotopes in

the air, water, rocks, plants

– Usually low and safe

10.1 RadioactivityHow does nuclear radiation effect people?

• Name the three types of nuclear radiation, describe what each is, and what is needed to protect yourself from them.

S-81What are three types of nuclear radiation?

• Nuclear radiation ionize atoms– Breaks the bonds holding molecules together– DNA, RNA strands get changes– Alpha – skin damage (not

serious unless inhaled or eaten)– Beta – damages body tissue – only surface– Gamma – damage body tissue – deep into

body– Symptoms – hair falls out, skin sloughs off,

vomiting,

10.1 RadioactivityHow does nuclear radiation effect people?

How can the amount of decay be calculated?

10.2 Rates of Nuclear Decay

• Nuclear Decay Rate– How fast nuclear change takes place– Half-Life – the time it takes for one half

of a sample to decay– After one half life – ½ the sample is still

there– After two half lives – ¼ – After three half lives – 1/8

10.2 Rates of Nuclear DecayHow can the amount of decay be calculated?

• Nuclear Decay Rate– Half lives can be from very high

• Uranium-238 (4,470,000,000 years)

– To very short• Radon-222 (3.82

days)

– These decay rates are constant• Independent of the amount of radioisotope

present

10.2 Rates of Nuclear DecayHow can the amount of decay be calculated?

• Nuclear Decay Rate– To calculate the amount of radioisotope

left we have to first calculate how many have lives have passed• Divide the total time by the half-life

– Multiply ½ that many times

10.2 Rates of Nuclear DecayHow can the amount of decay be calculated?

• Sample Problem– How many grams of Iridium-182 will be left

after 45 minutes. The half-life of Iridiu-182 is 15 minutes and the original sample was 5g

– First calculate the number of half-lives

– Now multiply out the ½ that many times

– Finally, multiply your original mass times this number

10.2 Rates of Nuclear DecayHow can the amount of decay be calculated?

Half-Life=45min/15minHalf-Life=3

½ x ½ x ½ = 0.1250.125 x 5 = 0.625g

• Sample Problem– How many grams of Radon-222 will be left

after 22.92 days. The half-life of Radon-222 is 3.82 days and the original sample was 126g

– First calculate the number of half-lives

– Now multiply out the ½ that many times

– Finally, multiply your original mass times this number

10.2 Rates of Nuclear DecayHow can the amount of decay be calculated?

Half-Life=22.92 days/3.82 daysHalf-Life=6

½ x ½ x ½ x ½ x ½ x ½ = 0.0156250.015625 x 126 = 1.97g

•Paper Airplane

S-82

S-84

No, the Test isn’t that hard

Really