1. Chapter 10 Radioactivity and Nuclear reactions

2. Radioactivity and Nuclear reactions
Chemical reactions occur by the rearrangement of electrons to make different bonds with other atoms
Nuclear reactions occur by a change in an atom’s nucleus (where the protons and neutrons are stored)
Radioactivity – the emission of subatomic particles or high-energy electromagnetic radiation by the nuclei of certain atoms

3. Isotope symbol A = Mass number, Sum of protons and neutrons in nucleus
Z = Atomic number, the number of protons in the nucleus
X = Chemical symbol
Certain Isotopes can be refered to as nuclides
11 neutrons and 10 protons
10 neutrons and 10 protons

4. Subatomic particle notation
Proton symbol
Neutron symbol
Electron symbol
Positron symbol
Mass number still in top left corner
Number of protons still in bottom left corner

5. Types of radioactivity
Alpha (α) decay – occurs when an unstable nucleus emits a particle consisting of two protons and two neutrons
This adds up to a helium nucleus
Alpha particle =
Can represent process through a nuclear reaction
Mass number and protons must be balanced

6. Alpha decay continuted
Highly energetic radiation (like alpha decay) can interact and damage other molecules (like biological molecules)
Alpha decay has the highest ionizing power due to its large size, but also has the lowest penetrating power because of its large size

7. Beta (β) decay
Beta (β) decay – when an unstable nucleus emits an electron
Through a neutron changing into a proton, an electron can be emitted from the nucleus
Remember that all protons and neutrons must still be balanced in the equation
Smaller size means less ionizing power, but better penetrating power

8. Gamma (γ) ray emission
Gamma (γ) rays – high energy short wavelength photons
Gamma ray symbol
Alpha emission also occurs with gamma emission
Has the lowest ionizing power, but the highest penetrating power

9. Positron Emission
Positron – the antiparticle of an electron, same mass but with opposite charge
When a proton changes into an neutron a positron is emitted
Positrons have the same ionization and penetration power as beta particles

10. Electron capture
Electron capture – when a nucleus assimilates an electron from an inner orbital of its electron cloud
A proton and an electron combine to make a neutron

12. Practice
Identify the emission types

13. Practice continued
Fill in the empty position to balance the nuclear equation, then identify type of radiation

14. Practice continued
Draw the equations for 238-uranium undergoing alpha decay, beta decay, positron emission, and electron capture

15. Half-life (t1/2)
Half-life – (t1/2) the amount it takes for half of a radioactive sample to decay.
Half-life is independent of size, temperature, and pressure
Half-life is different for every element

17. Practice
If you have 20g of carbon, how much will you have after one half life? How much after a total of two half-lifes?
If the half life of Cobalt-60 is 5.3 years, how many years will it take a 100g sample to decay to 25g?

18. Nuclear Fission Nuclear fission – splitting of atoms
Bombarding uranium (specifically U-235) with neutrons causes nuclear fission -- the splitting of the uranium atom
Process releases a large amount of energy
3 neutrons are produced that can cause 3 more U-235 isotopes to undergo fission, this is a chain reaction

19. Nuclear Fusion Nuclear Fusion – combining of atoms
Produces about 1000 times more energy than fission
Mechanism behind the hydrogen bomb

20. Chapter 10 Review Radioactivity Types of radioactive decay Half-life
Nuclear Fission and Fusion