1 nuclear chemistry active chemistry. 2 review atomic notation

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Nuclear Chemistry

Active Chemistry

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Review Atomic Notation

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Nucleons• Protons and Neutrons• The nucleons are bound together by the strong force.• Nucleons are made of Quarks which are considered to be

fundamental particles.

• Quarks bind together with gluons to make composite particles called hadrons.

• The most common examples of a hadron are neutrons and protons.

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Isotopes

• Atoms of a given element with:

same #protons

but

different # neutrons

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Isotopes of Carbon

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• 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.

Radioactive Isotopes

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Marie Curie: 1876-19341876-1934 born in Poland• Lived in France• 1898 discovered the elements

polonium and radium.• She discoveredShe discovered

radioactivityradioactivity, the , the spontaneous disintegration of spontaneous disintegration of some elements into smaller some elements into smaller pieces.pieces.

• Winner of 1903 Nobel Prize for Physics with Henri Becquerel and her husband, Pierre Curie.

• Winner of the sole 1911 Nobel Prize for Chemistry.•She died of aplastic anaemia, a blood disease that often results from exposure to large amounts of radiation.

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Nuclear Reactions vs. Nuclear Reactions vs. Normal Chemical Normal Chemical

ChangesChanges• Nuclear reactions involve the nucleusNuclear reactions involve the nucleus• The nucleus opens, and protons and The nucleus opens, and protons and

neutrons are rearrangedneutrons are rearranged• The opening of the nucleus releases a The opening of the nucleus releases a

tremendous amount of tremendous amount of energyenergy that holds that holds the nucleus together – called the nucleus together – called binding binding energyenergy

• ““Normal” Chemical Reactions involve Normal” Chemical Reactions involve electronselectrons, not protons and neutrons, not protons and neutrons

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Types of RadiationTypes of Radiation

e01

42He

• AlphaAlpha ( () – a positively ) – a positively charged (+2) helium isotopecharged (+2) helium isotope we usually ignore the charge because it we usually ignore the charge because it involves electrons, not protons and neutronsinvolves electrons, not protons and neutrons

•Beta Beta ((ββ) – an electron) – an electron

•GammaGamma ( (γγ) – pure energy; ) – pure energy; called a ray rather than a called a ray rather than a particleparticle

00

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Other Nuclear ParticlesOther Nuclear Particles

e01

n10• NeutronNeutron

• Positron – a positive Positron – a positive electronelectron

•Proton – usually referred to Proton – usually referred to as hydrogen-1as hydrogen-1

•Any other elemental isotopeAny other elemental isotope

H11

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Sheilding Ability Sheilding Ability ChemSaver p. 20ChemSaver p. 20

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XAZ

Mass Number

Atomic NumberElement Symbol

Atomic number (Z) = number of protons in nucleus

Mass number (A) = number of protons + number of neutrons

= atomic number (Z) + number of neutrons

A

Z

1p11H1or

proton1n0

neutron0e-1

0-1or

Beta0e+1

0+1or

positron4He2

42or

particle

1

1

1

0

0

-1

0

+1

4

2

ChemSaver p. 20

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Balancing Nuclear Equations

1. Conserve mass number (A).

The sum of protons plus neutrons in the products must equal the sum of protons plus neutrons in the reactants.

1n0U23592 + Cs138

55 Rb9637

1n0+ + 2

235 + 1 = 138 + 96 + 2x1

2. Conserve atomic number (Z) or nuclear charge.

The sum of nuclear charges in the products must equal the sum of nuclear charges in the reactants.

1n0U23592 + Cs138

55 Rb9637

1n0+ + 2

92 + 0 = 55 + 37 + 2x023.1

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Emission of alpha particles :

• helium nuclei • two protons and two neutrons • charge +2  • can travel a few inches through air• can be stopped by a sheet of paper,

clothing.

Alpha Decay

4He2

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or

particle

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Alpha Decay

Uranium Thorium

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Beta Decay

• Beta particles : electrons ejected from the nucleus when neutrons decay

n p+ +-

• Beta particles have the same charge and mass as

"normal" electrons.

0e-1

0-1

or

Beta

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Beta Decay

Thorium Protactinium

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Gamma Decay

• Gamma radiation 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.

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Transmutation

• Transmutation, or artificial radioactivity, is when you hit a nucleus with a projectile.

• If the projectile hits the nucleus at a great enough rate, the projectile and the nucleus will fuse together and make a larger nucleus. In most cases, the nucleus will eject a by-product particle.

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Tranmutation

• The target nucleus is the isotope which is bombarded (in the example above, the lead-207)

• The projectile is the particle fired at the nucleus (carbon-12)

• The product is the new nucleus produced by the reaction (francium-218)

• The ejected particle is the light nucleus or particle emitted in the reaction (hydrogen-1)

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Example: What is the product nucleus when a uranium-235 nucleus is hit with a hydrogen-2 nucleus, and a

neutron is ejected from the target?

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By the law of conservation of matter, the product side of the reaction should add up to the reactant side in

terms of the atomic number.

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Learning Check

What radioactive isotope is produced in the following bombardment of boron?

10B + 4He ? + 1n

5 2 0

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Learning Check

What radioactive isotope is produced in the following bombardment of boron?

10B + 4He 13N + 1n

5 2 7 0

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Write Nuclear Equations!

Write the nuclear equation for the beta emitter Co-60.

6060CoCo 00ee ++ 6060NiNi2727 -1 -1 2828

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Nuclear FissionNuclear Fission

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Nuclear FissionNuclear FissionFission Fission is the splitting of atomsis the splitting of atoms

These are usually very large, so that they are not as These are usually very large, so that they are not as

stablestable

ChemSaver p. 20

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Representation of a fission process.

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Nuclear Fission & Nuclear Fission & POWERPOWER

• Currently about 103 Currently about 103

nuclear power plants in nuclear power plants in

the U.S. and about 435 the U.S. and about 435

worldwide.worldwide.

• 17% of the world’s 17% of the world’s

energy comes from energy comes from

nuclear.nuclear.

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Figure 19.6: Diagram of a nuclear power plant.

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Nuclear Fusion

Fusion nuclei combine to form a more massive nucleus

2H + 3H 4He + 1n +

1 1 2 0

Occurs in the sun and other stars

Energy

ChemSaver p. 20