1. V. Radioactivity

2. Recall…Parts of an Atom
3 Parts of the Atom, their location, charge, and mass
Electron
around the nucleus (electron cloud)
negative
~0 amu
Proton
in the nucleus
positive
1 amu
Neutron
In the nucleus
neutral

3. Recall… Atomic Attributes
# of protons
# of electrons (in a neutral atom)
Mass #
Mass of an atom
#p+ + #no

4. Recall… What tells us the identity of the element (atom)?
Convert Hydrogen – 3 to nuclear notation

5. Recall…Isotope Naming
Isotope (hyphen) Notation
Element Name – mass #
Ex: Carbon – 12 or Neon – 22
Nuclear Notation H 3 1

6. A. Nuclear Reactions
Nuclear Reaction = the nucleus of an atom changes and becomes a new ELEMENT.

7. B. Nuclear Reactions
In a nuclear reaction, unstable nucleus changes (LOSES MASS AND ENERGY) to become more stable
Unstable if too many or few neutrons

8. C. Radioactivity Mother of Radioactivity = Marie Curie (1867 – 1934)
2 Nobel Prizes
Showed rays emitted by uranium atoms caused fogging in photographic plates
Named this process radioactivity
Radioactive particles called radiation

9. C. Radioactivity
Radioactivity – the process by which some substances spontaneously emit energy called radiation
Radiation – penetrating rays/particles emitted by a radioactive substance
Radioactive Decay – An unstable nucleus spontaneously loses energy by emitting radiation

10. D. Types of Radiation
Alpha Radiation
Beta Radiation
Gamma Radiation

11. 2 4 He (positive charge of 2+)
E. Alpha Radiation
Alpha (α) particles released
α particle = Helium Nucleus (2 protons, 2 neutrons, and 0 electrons)
2 4 He (positive charge of 2+)
Produced in large nuclei

12. −1 0  or −𝟏 𝟎 e (negative charge of 1–)
F. Beta Radiation
Beta (ß) particles released
ß particle = high speed electron leaves nucleus
−1 0  or −𝟏 𝟎 e (negative charge of 1–)
Occurs in elements with more neutrons than protons: a neutron splits into a proton and electron.

13. 0 0  (zero charge) G. Gamma Radiation Gamma Ray () released
 ray = high energy radiation
0 0  (zero charge)
Occurs if nucleus is in an excited state and it releases energy (gamma rays).
Usually occurs with alpha or beta decay.

14. Summary – 3 Types of Radiation
Radiation Type
Symbol
Mass (amu)
Charge
Alpha 
2 4 He 4 2+
Beta 
−1 0 e
~0 (very small) 1-
Gamma 
0 0 

15. H. Radiation Alpha particles = stopped by paper.
Beta particles = stopped by wood
Most (but not all) Gamma rays = stopped by lead or thick concrete.
alpha particles least penetrating, gamma particles most penetrating.