1. Test over: Periodic Table Structure Pg. 30 Periodic Families Pg. 31
Periodic Trends Pg. 32
Periodic Trends Notes Pg. 33

2. Add to table of contents:
Nucleus-Radioactivity Pg. 34
Nuclear Chemistry Pg. 35

3. Nuclear
Chemistry

4. The Discovery of Radioactivity
Antoine-Henri Becquerel designed an experiment to determine if phosphorescent minerals also gave off x-rays.

5. The Discovery of Radioactivity, Continued
Bequerel discovered that certain minerals were constantly producing penetrating energy rays he called uranic rays.
Like x-rays.
But not related to fluorescence.
Bequerel determined that:
All the minerals that produced these rays contained uranium.
The rays were produced even though the mineral was not exposed to outside energy.
Energy apparently being produced from nothing?

6. The Discovery of Radioactivity, Continued
Marie Curie used an electroscope to detect the radiation of uranic rays in samples.
By carefully separating minerals into their components, she discovered new elements by detecting the radiation they emitted.
Radium named for its green phosphorescence.
Polonium named for her homeland.
Since the radiation was no longer just emitted from of uranium, she renamed it radioactivity.

7. What Is Radioactivity?
Radioactivity = release of tiny, high-energy particles from an atom.
Particles are ejected from the nucleus.

8. Properties of Radioactivity
Radioactive rays can ionize matter.
Cause uncharged matter to become charged.
Radioactive rays have high energy.
Radioactive rays cause phosphorescent chemicals to glow.
Types of Radioactive Rays:
Alpha (ά)
Beta (β)
Gamma (γ)
Positron (b+)

9. Alpha Emission (Decay)
An ά particle contains 2 protons and 2 neutrons.
Helium nucleus.
Stopped by skin or sheet of paper
Loss of an alpha particle means:
Atomic number decreases by 2.
Mass number decreases by 4.

10. ά Decay

11. Beta Emission (Decay) A β particle is like an electron, BUT
Moving much faster
Produced from the nucleus
Stopped by few sheets of aluminum foil or glass
When an atom loses a β particle, its:
Atomic number increases by 1
Mass number remains the same
In beta decay, a neutron changes into a proton

12. β Decay

13. Gamma Emission Gamma (ϒ) rays are high-energy photons of light
Stopped by several centimeters of lead
No loss of particles from the nucleus
No change in the atomic number and mass number
Does not occur alone
Will accompany an α or β decay

14. Positron Emission (Decay)
Positron has a charge of 1+ c.u. and negligible mass.
Anti-electron.
When an atom loses a positron from the nucleus, its:
Mass number remains the same.
Atomic number decreases by 1.
Positrons appear to result from a proton changing into a neutron.

15. Positron b+ Decay

16. g a, b, He e Types of Radiation Symbol 4 0.00055 Charge +2 -1
Type of Radiation
Alpha particle
Beta particle
Gamma ray
Symbol a, b, g
Mass (amu) 4
Charge +2 -1 4 He e 2 -1

17. Penetrating Ability Alpha particle stopped by skin or sheet of paper
Beta particle stopped by few sheets of aluminum foil
Gamma ray stopped by several centimeters of lead

18. Important Atomic Symbols
Particle
Symbol
Nuclear symbol
Proton p+
Neutron n0
Electron e-
Alpha a
Beta
b, b-
Positron
b, b+