1 intro to nuclear chemistry

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Intro to Nuclear Chemistry

Chemistry Mrs. Coylehttp://www.chem.orst.edu/graduate/pics/Reactor.jpg

How does a nuclear reactor work?

http://www.lanl.gov/science/1663/images/reactor.jpg

How does a small mass contained in this bomb cause Nuclear Bomb of 1945 known as fat man

http://www.travisairmuseum.org/assets/images/fatman.jpg

this huge nuclear explosion?

http://library.thinkquest.org/06aug/01200/Graphics/705px-Nuclear_fireball.jpg

Is there radon in your basement?

http://a.abcnews.com/images/Blotter/abc_1radon_ad_070625_ssh.jpg

Notation

Nucleons Protons and Neutrons

The nucleons are bound together by the strong force.

Isotopes Atoms of a given element with: same #protons but different # neutrons

H

H

H

http://education.jlab.org/glossary/isotope.html

Isotopes of Carbon

Radioactive Isotopes Isotopes of certain unstable elements that spontaneously emit particles and energy from the nucleus.

Henri Beckerel 1896 accidentally observed radioactivity of uranium salts that were fogging photographic film. His associates were Marie and Pierre Curie.

Marie Curie: born 1867, in Poland as Maria Sklodowska Lived in France 1898 discovered the elements polonium and radium.

http://www.radiochemistry.org/nuclearmedicine/pioneers/images/mariecurie.jpg

Marie Curie a Pioneer of Radioactivity Winner of 1903 Nobel Prize for Physics with Henri Becquerel and her husband, Pierre Curie. Winner of the sole 1911 Nobel Prize for Chemistry.

3 Main Types of Radioactive Decay Alpha Beta a b

Gamma g

Alpha DecayEmission of alpha particles a : helium nuclei two protons and two neutrons charge +2e can travel a few inches through air can be stopped by a sheet of paper, clothing.

Alpha Decay

Uranium

Thorium

Alpha Decay

http://education.jlab.org/glossary/alphadecay.gif

Beta Decay Beta particles b: electrons ejected from the nucleus when neutrons decay ( n p+ +b- ) Beta particles have the same charge and mass as "normal" electrons.

Beta Decay Beta particles b: electrons ejected from the nucleus when neutrons decay n p+ +b Beta particles have the same charge and mass as "normal" electrons. Can be stopped by aluminum foil or a block of wood.

Beta Decay

Beta Decay

Thorium

Protactinium

Gamma Decay Gamma radiation g : electromagnetic energy that is released. Gamma rays are electromagnetic waves. They have no mass. Gamma radiation has no charge. Most Penetrating, can be stopped by 1m thick concrete or a several cm thick sheet of lead.

Examples of Radioactive DecayAlpha Decay Po Pb + He e

Beta Decay p n + n p + e C N + e Gamma Decay Ni Ni + g (excited nucleus)

Which is more penetrating? Why?

Part IINuclear Stability Half-Life

Nuclear Stability Depends on the neutron to proton ratio.

Band of Stability

Number of Neutrons, (N)

Number of Protons (Z)

What happens to an unstable nucleus? They will undergo decay The type of decay depends on the reason for the instability

What type of decay will happen if the nucleus contains too many neutrons? Beta Decay

Example:14 6

C

14

N

+

0 -1

e

7

In N-14 the ratio of neutrons to protons is 1:1

Nuclei with atomic number > 83 are radioactive

Radioactive Half-Life (t1/2 ): The time for half of the radioactive nuclei in a given sample to undergo decay.

Common Radioactive IsotopesIsotope Half-Life Radiation Emittedb, g a

Carbon-14 Radon-222

5,730 years 3.8 days

Uranium-235Uranium-238

7.0 x 108 years4.46 x 109 years

a, ga

Radioactive Half-Life After one half life there is 1/2 of original sample left. After two half-lives, there will be 1/2 of the 1/2 = 1/4 the original sample.

Graph of Amount of Remaining Nuclei vs TimeA=Aoe-lt

A

ExampleYou have 100 g of radioactive C-14. The half-life of C-14 is 5730 years. How many grams are left after one halflife? Answer:50 g How many grams are left after two halflives?

ProblemA sample of 3x107 Radon atoms are trapped in a basement that is sealed. The half-life of Radon is 3.83 days. How many radon atoms are left after 31 days? answer:1.2x105 atoms