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Normal Chemical Changes Nuclear reactions involve the nucleus The nucleus opens, and protons and neutrons are rearranged The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called binding energy “Normal” Chemical Reactions

Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

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Page 1: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclear Reactions vs. Normal Chemical

ChangesNuclear reactions involve the

nucleus

The nucleus opens, and protons and neutrons are rearranged

The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called binding energy

“Normal” Chemical Reactions involve electrons, not protons and neutrons

Page 2: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

The Nucleus

Remember that the nucleus is comprised of the two nucleons, protons and neutrons.

The number of protons is the atomic number.

The number of protons and neutrons together is effectively the mass of the atom.

Page 3: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Isotopes

Not all atoms of the same element have the same mass due to different numbers of neutrons in those atoms.

There are three naturally occurring isotopes of uranium:Uranium-234Uranium-235*Uranium-238

Page 4: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclide Symbols

Page 5: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclide Symbols

Page 6: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 7: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

IsotopesTwo Categories

Unstable – isotopes that continuously and spontaneously break down/decay in other lower atomic weight isotopes

Stable – isotopes that do not naturally decay but can exist in natural materials in differing proportions

Page 8: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

RadioactivityIt is not uncommon for some

isotopes of an element to be unstable, or radioactive.

We refer to these as radioisotopes.

There are several ways radioisotopes can decay and give off energy known as radiation.

Page 9: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 10: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 11: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Types of Radioactive Decay Alpha Decay

Loss of an -particle (a helium nucleus)

He42

U23892

Th23490 He4

2+

Page 12: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Types of Radioactive Decay Beta Decay

Loss of a -particle (a high energy electron)

0−1 e0

−1or

I13153 Xe131

54 + e0

−1

Page 13: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Types of Radioactive Decay Gamma Emission

Loss of a -ray (high-energy radiation that almost always accompanies the loss of a nuclear particle)

00

Page 14: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Types of Radiation

e01

He42

• Alpha (ά) – a positively charged helium isotope - we usually ignore the charge because it involves electrons, not protons and neutrons

•Beta (β) – an electron

•Gamma (γ) – pure energy; called a ray rather than a particle

Page 15: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Penetrating Ability

Page 16: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 17: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 18: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 19: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 20: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 21: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Geologic Time Radioactive Isotopes used in Geologic Dating

Parent Daughter half-life (y)

U-238 Lead-206 4.5 billion

U-235 Lead-207 713 million

Thorium 232 Lead 208 14.1 Billion

K-40 Argon-40 1.3 billion

R-87 Sr-87 47 billion

C-14 N-14 5730

Half-life = time it takes for 1/2 of the parent mass to decay into the daughter mass

Page 22: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 23: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Geologic Time

14Carbon Dating

Dating is accomplished by

determining the ratio of 14C to non-

radioactive 12C which is constant in

living organisms but changes after the

organism dies

When the organism dies it stops taking in 14C which disappears as it decays to 14N

Page 24: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 25: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 26: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons
Page 27: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Forensic 14Carbon Cases

Dead Sea Scrolls – 5-150 AD

Stonehenge – 3100 BC

Hezekiah’s Tunnel - 700 BC

Page 28: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Forensic 14Carbon Cases

● King Arthur’s Table in Winchester Castle, England 14C dated to 13th

century AD

● Cave painting at Lascaux, France

14C dated to 14,000 BC

● Rhind Papyrus on Egyptian math 14C dated to 1850 BC

Page 29: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Forensic 14Carbon Cases

●The Shroud of Turin was

14C dated 1260-1390 AD

which suggests that it is a fake

● However, recent evaluation

shows that the sample measured

was from a medieval patch and/or

that it was seriously contaminated

with molds, waxes, etc

●New estimates date the shroud from

1300-3000 ybp bases on vanillin

retention

Page 30: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Forensic 14Carbon CasesNuclear testing during 1955-63 put large amounts of 14C into the atmosphere which was incorporated into the enamel of human teeth. Because such testing stopped the 14C input ended and the 14C in the teeth decayed at a fixed rate allowing dating of the teeth

Page 31: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclear ReactionsAlpha emission

Note that mass number goes down by 4 and atomic number goes down by 2.

Nucleons (nuclear particles… protons and neutrons) are rearranged but conserved

Page 32: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclear ReactionsBeta emission

Note that mass number is unchanged and atomic number goes up by 1.

Page 33: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Write Nuclear Equations!Write the nuclear equation for the

alpha decay of radon-222

222Rn 218Po + 4He

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

60Co 60Ni + 0e

8486 2

27 28 -1

Page 34: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

BellringerFill in Chart

Radioactive Particle Nuclear Symbol Pertinent Information

alpha

beta

gamma

positron

4

He2

0

e-1

0

γ0

0

e+1

helium atom without any electrons

high energy electron, no mass with a negative charge

high energy ray with no mass and no atomic number

mass of an electron but a positive charge

Page 35: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Neutron-Proton RatiosAny element with more than

one proton (i.e., anything but hydrogen) will have repulsions between the protons in the nucleus.

A strong nuclear force helps keep the nucleus from flying apart.

Neutrons play a key role stabilizing the nucleus.

Therefore, the ratio of neutrons to protons is an important factor.

Page 36: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Stable Nuclei

The shaded region in the figure shows what nuclides would be stable, the so-called belt of stability.

Page 37: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Neutron-Proton Ratios

For smaller nuclei (Z 20) stable nuclei have a neutron-to-proton ratio close to 1:1

Page 38: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Neutron-Proton Ratios

As nuclei get larger, it takes a greater number of neutrons to stabilize the nucleus.

Page 39: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Stable Nuclei

Nuclei above this belt have too many neutrons.

They tend to decay by emitting beta particles.

Page 40: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Stable Nuclei

Nuclei below the belt have too many protons.

They tend to become more stable by positron emission or electron capture.

Positron = 0e+1

Page 41: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Stable Nuclei

There are no stable nuclei with an atomic number greater than 83.

These nuclei tend to decay by alpha emission.

Page 42: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Radioactive Series

Large radioactive nuclei cannot stabilize by undergoing only one nuclear transformation.

They undergo a series of decays until they form a stable nuclide (often a nuclide of lead).

Page 43: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclear TransformationsNuclear transformations can be induced by accelerating a particle and colliding it with the nuclide.

These particle accelerators are enormous, having circular tracks with radii that are miles long.

Page 44: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Measuring Radioactivity

One can use a device like this Geiger counter to measure the amount of activity present in a radioactive sample.

The ionizing radiation creates ions, which conduct a current that is detected by the instrument.

Page 45: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Energy in Nuclear ReactionsThere is a tremendous amount of energy stored in

nuclei.

Einstein’s famous equation, E = mc2, relates directly to the calculation of this energy.

In chemical reactions the amount of mass converted to energy is minimal.

However, these energies are many thousands of times greater in nuclear reactions.

Page 46: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclear FissionHow does one tap all that energy?

Nuclear fission is the type of reaction carried out in nuclear reactors.

Page 47: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclear Fission

Bombardment of the radioactive nuclide with a neutron starts the process.

Neutrons released in the transmutation strike other nuclei, causing their decay and the production of more neutrons.

This process continues in what we call a nuclear chain reaction.

Page 48: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

Trafficking Nuclear Materials

Page 49: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

Man-made Radioactive Isotopes

Smuggled Plutonium – can identify the reactor type in which the fuel was originally radiated and the type of plant where the material was subsequently reprocessed

In 1997, two pieces of stainless steel contaminated with alpha-emitters were found in a scrap metal yard in Germany.

Source was identified as a fast-breeder reactor in Obninsk, Russia

Page 50: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

Weapons-grade Plutonium

The isotopic composition of plutonium can indicate INTENT

In 1994, a small lead cylinder discovered in a garage in Tengen on the Swiss-German border was found to contain plutonium metal, isotopically enriched to 99.7%

Weapons-grade Pu-239

Page 51: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

Radioactive Fingerprints

Preserving the conventional chain of evidence whilst dealing with radioactive samples can be problematic

For example – lifting fingerprints and swiping for radioactive contamination cannot both be carried out

The first ever radioactive fingerprint has recently been identified on an object contaminated with alpha-emitting isotopes

Page 52: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

If there are not enough radioactive nuclides in the path of the ejected neutrons, the chain reaction will die out.

Therefore, there must be a certain minimum amount of fissionable material present for the chain reaction to be sustained: Critical Mass.

Page 53: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclear ReactorsIn nuclear reactors the heat generated by the reaction is used to produce steam that turns a turbine connected to a generator.

Page 54: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclear ReactorsThe reaction is kept in

check by the use of control rods.

These block the paths of some neutrons, keeping the system from reaching a dangerous supercritical mass.

Page 55: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Nuclear Fusionnuclear fusion is a nuclear reaction in

which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus.

During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy which is released.

Fusion is the process that powers active stars.

Fusion would be a superior method of generating power.The good news is that the

products of the reaction are

not radioactive.The bad news is that in order to achieve fusion, the material

must be in the plasma state at several million kelvins.

Page 56: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Weapons whose explosive output is exclusively from fission reactions are commonly referred to as atomic bombs or atom bombs

misnomer because the energy actually comes from nucleus

Many fission products are either highly radioactive (but short-lived) or moderately radioactive (but long-lived), and as such are a serious form of radioactive contamination if not fully contained. Fission products are the principal radioactive component of nuclear fallout.

Page 57: Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus Nuclear reactions involve the nucleus The nucleus opens, and protons

Thermonuclear bombs work by using the energy of a fission bomb to compress and heat fusion fuel.

When the fission bomb is detonated, gamma rays and X-rays emitted first compress the fusion fuel, then heat it to thermonuclear temperatures

Tsar Bomb