1. Nuclear Chemistry
Chapter 10

2. Chemical Rxn vs. Nuclear Rxn
Chemical reactions involve valence ELECTRONS
Nuclear reactions involve PROTONS and NEUTRONS

3. Chemical Energy Energy stored in the chemical bonds of a substance
Chemical reactions involve the breaking of chemical bonds in the reactants and the formation of chemical bonds in the products
During this process, energy is either released (exothermic) or absorbed (endothermic)

4. Radioactivity
The process in which an unstable atomic nucleus emits charged particles and energy
An atom that has an unstable nucleus is called a Radioactive isotope, or Radioisotope
Carbon-14 is an example of a radioisotope
Radioisotopes spontaneously change in to other isotopes over time
This is called NUCLEAR DECAY and can result in the formation of an entirely different element than the original element

6. Historical Figures Jigsaw
What important discovery was made by Wilhelm Roentgen?
What material did Antoine Becquerel work with in his own investigations of X rays?
What did Becquerel discover through his experiments?
What two elements were discovered by Marie and Pierre Curie?
Why is Ernest Rutherford considered the father of nuclear physics? List Rutherford's major achievements.

7. Radioactivity (The Good, The Bad)
Safari Montage

8. Nuclear Force
The attractive force that binds protons and neutrons together in the nucleus
Extremely weak at most distances, BUT over the very short distances present in an atom’s nucleus, the nuclear force is greater than the repulsive electrical force among protons
When the attractive nuclear force and the repulsive electrical force are not balanced, the nucleus of the atom is UNSTABLE

9. How does a nucleus become stable?
Through radioactive (or nuclear) decay!
Radiation is emitted from the unstable nucleus in the form of fast-moving particles and energy
This results in new nucleus and thus the identity of the element changes
Atoms that have an unstable nucleus are called radioactive isotopes

10. Nuclear Radiation
Charged particles and energy that are emitted from the nuclei of a radioactive isotope
Types
Alpha Particles – Least penetrating, travel only a few centimeters in air, can be stopped by clothes or a sheet of paper
Beta Particles – More penetrating than alpha particles, pass through paper, stopped by thin sheet of metal
Gamma Radiation – Much more penetrating than alpha and beta particles, need several centimeters of lead or several meters of concrete to stop gamma radiation

11. Alpha Decay Alpha Particle
Positively charged particle made up of two protons and two neutrons
Has a charge of +2
QUESTION: If an alpha particle has two protons, which element does is resemble?

12. Alpha Decay Alpha particles are represented by
This type of nuclear reaction can be expressed as an equation (write in the parts of the equation below):

13. Beta Particles An electron emitted by an unstable nucleus
Has a mass number of (0) and a charge of (-1)

14. Beta Decay
During Beta Decay, ONE neutron decays into ONE proton and ONE electron
The PROTON stays trapped in the nucleus and the ELECTRON is released
What does this mean?
The product isotope has ONE proton more and one neutron fewer than the reactant isotope, but the mass numbers are the same because electrons have NO mass.

15. Gamma Radiation
A penetrating ray of energy emitted by an unstable nucleus
Has no mass and no charge
Travel through space at the speed of light
Can easily pass through the human body

16. Ionizations
The process of stripping, knocking off or otherwise removing electrons from their orbital paths
This creates free negatively-charged electrons and leaves nuclei that have a positive charge
These particles can interact with other materials to produce changes in materials (like our body)
If this happens in our cells, cellular damage may result

17. Nuclear Power
How it Works
Chernobyl Disaster

18. Sources of Radiation Background Radiation
Nuclear radiation that occurs naturally in the environment
Examples: Air, water, rocks, plants, animals, cosmic rays
Cosmic rays
Streams of charged particles from outer space
Nuclear Radiation in the body
Because particles and energy can ionize cells in the human body, they can break apart the bonds holding DNA and proteins together
If these molecules change, cells may no longer function how they are supposed to
Radon Gas
Emits alpha particles, can cause lung cancer
Formed through a series of nuclear decays that begins with uranium-238 deep underground
Radon gas seeps upwards and can accumulate in basements that don’t have proper ventilation

19. Geiger Counters Used to detect nuclear radiation
Uses a gas-filled tube to measure ionizing radiation
Nuclear radiation enters tube, the gas in the tube is ionized and generates an electric current, which can be measured
More nuclear radiation = greater electrical current

20. Group Discussion What is nuclear decay?
What is emitted from a radioactive isotope during radioactive decay?

21. Half-life Nuclear Decay Rate
Refers to how fast nuclear changes take place in a radioactive substance
Constant for a given radioactive isotope
The length of time necessary for half of the atoms of a sample material to decay
Half of the atoms have decayed, half remain the same
Range from fractions of a second to billions of years for long-lived materials

22. Radiocarbon Dating http://www.youtube.com/watch?v=phZeE7Att_s
The age of an object is determined by comparing the object’s carbon-14 levels with carbon-14 levels in the atmosphere
Used to date fossils up to 50,000 years old
Why does this work?
Plants absorb carbon dioxide from the atmosphere during photosynthesis
While alive, they maintain the same ratio of Carbon-14 to Carbon 12 as in the atmosphere
Animals have the same ratio of C-14 to C-12 as the plants they eat
Once a plant or animal dies, it no longer absorbs carbon and so the remaining C-14 begins to decay