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Nuclear Chemistry. Nuclear Power Plant in Richland, WA. The Band of Stability. Certain isotopes are more stable than others The ratio of protons to neutrons is important in determining stability Example: Mg has 12 neutrons and 12 protons, U has 146 neutrons for 92 protons .

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Nuclear Chemistry

Nuclear Power Plant in Richland, WA


The Band of Stability

  • Certain isotopes are more stable than others
  • The ratio of protons to neutrons is important in determining stability
  • Example: Mg has 12 neutrons and 12protons, U has 146 neutrons for 92 protons

Review From

Tuesday’s Lesson


Elements on the edge of

  • the band or outside of the
  • band are radioactive.
  • Radioactive isotopes
  • usually have more than
  • 83 protons.
what holds the nucleus together
What holds the nucleus together?
  • Strongnuclear force (attractive)
  • Force pushing protons apart = repulsion due to positive charge (electrostatic force)
    • Protons: contribute to both the attractive force (strong force) and repelling force (charge)
    • Neutrons: contribute to the strong force (attractive) while having no charge. Act as the “glue” to bind the nucleus together

Binding Energy: Energy needed to hold the protons in the nucleus together (Also the energy released when an atom is split).

mass and energy
Mass and energy
  • During nuclear reactions, there is actually a small change in mass

238.0003 g

233.9942 g + 4.0015 g = 237.9957



Mass Defect: Measured mass of an atom is LESS THAN the sum of the masses of its particles.

E = mc2

Binding Energy


Speed of Light

how can we form a new element
How can we form a new element?
  • Must have a stable nucleus and exist long enough to be detected.
  • The neutron to proton ratio is an important factor in determining the stability of a nucleus.
  • Some isotopes are more stable than others. Unstable isotopes undergo nuclear decay to produce atoms with lower mass.

Nuclear Chemistry!

Nuclear chemistry: the study of the nucleusof the atom.

(so, it involves neutrons and protons, not electrons!)


Chemical vs. Nuclear Reactions

Chemical Reactions: # of atoms of each element remains unchanged

Example: 2H2 + O2 2H2O

  • Nuclear Reactions: Affect the nucleus of the atom—rearrangements of protonsand neutrons.
  • **Sometimes the rearrangements lead to unstable or radioactiveelements.

Radioactive Decay—Spontaneous breakdown of an atom which results in the emission of particles, energyor both.

stability is relative
Stability is relative
  • Some radioactive elements take thousands or millions of years to decay
  • Some radioactive elements take days, minutes, or fractions of a second to decay
radioactive decay is measured in half lives
Radioactive decay is measured in Half-lives

Half-life: length of time it takes for halfof a starting amount of an element to decay

Ex. Radium has a half-life of 1,620 years

How many years?

1620 years

100 Radium


1620 years

50 Radium atoms

25 Radium atoms

half life cont
Half-life cont.

A shorter half-life means an element is more radioactive because the radioactivity is released faster.

Ex. Which element is more radioactive?

Carbon-14 (half-life 5,720 years) or Radium-226 (half-life 1,620 years)?


your turn
Your turn!

You have a sample of 200 radioactive atoms and the half life is 20 years. After 100 years, how many atoms will be left?

100/20 = 5 half lives

200  100  50  25  12.5  6.25 atoms (SO 6 ATOMS because you can’t have 0.25 of an atom!)


Real World use of Half-Lives: Radioactive Dating

  • Ratio of carbon 12 to carbon 14 used to determine age of once-living things! (Carbon-14 has a half-life of 5,730 years)
  • Uranium-238 has a half-life of 4.5 billion years so is used to date rocks
3 types of radiation
3 types of Radiation
  • Alpha (a) Radiation
  • Beta (b) Radiation
  • Gamma (g) radiation

Types of Decay: The Particles


1. Alpha positivecharge


Same as a Heliumnucleus

Alpha particle: two protons and two neutrons

Alpha particles are so large they cannot penetrate very far into matter (they can be shielded with a piece of paper!!)


Tho-Radia Face Cream

Promising instant curative and beautifying effects, Tho-Radia gained wide popularity in France during the early 1930's as a range of beauty products and perfumes. The face cream was especially popular and contained of 0.5g thorium chloride and 0.25mg radium bromide per 100g. It was even advertised as a creation of ‘Dr. Alfred Curie' although he was not a member of the Curie family and probably never existed.


Manufactured from 1918 to 1928 by the Bailey Radium Laboratories, Radithor was a well-known patent tonic that consisted of triple distilled water containing at a least one microcurie of Radium 226 and 228 isotopes. Said to cure stomach cancer and mental illness, it was even advertised as ‘Perpetual Sunshine' until it gained notoriety when Eben Byers, an American industrialist, drank a bottle a day for four years and consequently died in excruciating pain as cancer of the jaw caused his facial bones to disintegrate.

Radioactive Drinking Water

Ceramic jars that added radon to drinking water were popular during the early part of the 20th century. Revigator advertised itself as ‘nature's way to health' and its ores gave off millions of tiny rays of radiation that penetrated the water, creating ‘healthful radioactive water'.


Radioactive Toy Set

The Atomic Energy Lab first went on sale in 1951 and featured low levels of genuine radioactive material for children to experiment with. It remained on sale until the late 1970's and although the materials were labeled as ‘safe' you wouldn't find many parents today willing to let their kids play with uranium ore.


Radium Chocolate

Radium Chocolate manufactured by Burk & Braun was sold in Germany from 1931 to 1936, advertised for its powers of rejuvenation.


Types of Decay: The Particles


  • 2. Beta negativecharge


An electron is emitted and a neutron is converted into a proton!

beta particles =

high energy electrons

Beta particles also are a bit too large to penetrate you, and can be stopped with aluminum foil.


Types of Decay: The Particles

3. Gamma—high energy radiation

  • High energy electromagnetic radiation
  • No mass or charge
  • Often emitted along with beta or alpha radiation

Gamma rays penetrate, but can be stopped with lead (like x-rays!)

alpha decay
Alpha Decay
  • Atom releases an alpha particle.
  • Atomic # decreases becoming new element.


  • Notice:
  • total starting mass equals total resulting mass: 238 = 234 + 4
  • total starting charge equals total resulting charge: 92 = 90 + 2

alpha particle

Conclusion: in alpha decay a nucleus splits into two smaller elements, one of which is always a helium nucleus


Balancing Nuclear Equations

Your turn!

Alpha Decay










beta decay
Beta Decay
  • Atom releases a beta particlewith zero mass & negative charge
  • Atomic number increases (becomes new element!)


  • Notice:
  • total mass stays the same: 14 = 14 + 0
  • total charge stays the same: 6 = 7 - 1

Balancing Nuclear Equations

Beta Decay










An electron is emitted and a neutron is converted into a proton!


More Practice!

Francium-221 undergoes alpha decay. Write the nuclear reaction below.











Thorium-234 emits a beta particle. Write the nuclear reaction below.












The road to stability may be long!

  • Things to notice:
  • There are multiple steps
  • some steps are alpha decay, some are beta decay
  • the stable end point is an element with atomic # less than 83 (lead)
  • there are also unstable lead isotopes which are intermediates

What are some uses for radioactive elements??

Atomic Weapons

Nuclear Medicine

Nuclear Power


Radiation Therapy

  • Used to treat cancer(but yes, too much radiation can actually CAUSE cancer)
  • Mechanism: Radiation beams knock off electronsfrom atoms making up DNA chains and turn them into free radicals (damaging them!)
  • Polonium, Cobalt, Cesium & Radium are all elements used in radiation therapy.

Nuclear Power

  • Fission—Splitting of a heavy nuclei (like Uranium) **The products are radioactive.


  • Splitting one nucleus into smaller fragments
  • Nuclear power plants and most nuclear weapons rely on nuclear fission

Nuclear Power

  • Fusion—Combining of 2 or more lightnuclei (H + H  He) **Non-radioactive products. **Requires extremely high temperatures (sun/stars)

Both release LARGE amounts of ENERGY!


What is a Chain Reaction?

Chain Reaction: A reaction in which the material that starts the reaction is also one of the products and can start another reaction.

  • Two nuclei combine
  • Release large amounts of energy, but requires very high temperatures
    • At such high temperatures, nuclei are moving so fast that collisions between them can overcome the natural repulsion of their positive charges.
  • Examples
    • The Sun
    • The Hydrogen bomb
heat produces steam generating electricity



Steam produced




Heat Produces Steam, Generating Electricity

What are they?

Nuclear weapons derive their destructive force from nuclear fusionor fission.


How many have there been?

Two nuclear weapons have been detonated—both by the United States at the end of World War II.

Where were these weapons dropped?



  • August 6th, 1945
  • Uranium
  • 140,000 people killed (instantly,
  • or from illness associated with radiation)


  • August 9th, 1945
  • Plutonium
  • 80,000 people killed (instantly, or from illness associated with radiation)

Manhattan Project


  • The project to develop the first nuclear weapon during WWII (U.S., Canada & the U.K.)
  • Robert Oppenheimer: Scientific researcher (Father of the Atomic Bomb)
  • 1945—TrinityTest (First detonation of a nuclear bomb) in New Mexico


2 Main Types of Nuclear Weapons:

#1: Nuclear Fission—(Atomic Bombs)


2 Main Types of Nuclear Weapons:

#2: Nuclear Fusion—(Hydrogen Bombs)

  • Use the energy of a fission bomb to heat the fusion fuel
  • Over 1,000 times more powerful than a fission bomb!
  • Only 6 countries have detonated one: U.S., Russia, U.K., China, France, and India

Nuclear Fallout—What is it?

Nuclear fallout: the residual radiationhazard from a nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion.

hotter stars will produce larger elements
Hotter stars will produce largerelements

“Big Bang” = H & He

  • Cooler Stars = fuse H atoms into He
  • Bigger/Hotter stars = slightly heavier elements made, up to Fe
  • Supernova (explosion of star) = create heaviest elements (up to U)

Video clip: minutes 55:30 to 58

Some light to medium-sized elements formed by simple fusion of two elements

Elements heavier than iron are believed to be made by neutroncapture. This is a two-step process

Neutron collides and fuses with the nucleus of an atom

When the nucleus is overloaded with these neutrons, it will undergo betadecay (a neutron will turn into a proton)

Nucleosynthesis: forming new elements


Note: to find the product of a fusion reaction,

Add up the mass #’s and atomic #’s of your starting elements

Example from p92 in book

Step 1: Fusion with neutrons



Step 2: beta decay, creation of proton