1. Day 8
Chapter 4 Section 4

2. Mass Number Isotopes have different mass numbers
The mass # is the sum of the protons and neutrons.
(# protons) + (# neutrons) = mass number
Example: Potassium has 3 isotopes.
This is 3 different versions of the same atom
Each version has a different # of neutrons

3. What does this mean? Example… Potassium (K) 19
How many protons does potassium always have… 19
How many electrons does potassium have…
How many neutrons does potassium have…
There are 3 different #s of neutrons…that’s what makes the isotope.

4. K K K 39 19 40 41 19 19 How to write Isotopes Potassium – 39
1st
Potassium – 39
Potassium – 40
Potassium – 41
2nd
Mass # K 39 19 40 K 41 K 19 19
Proton #

5. Check
Determine the number of protons, electrons and neutrons for the following isotopes.
Neon-22
Calcium-46
Oxygen-17
Iron-57
Zinc-64
Mercury-204

6. amu…Atomic Mass Unit Example…Chlorine
Weighted average mass of the isotopes…?
Example…Chlorine
Atomic Mass of amu (periodic Table)
75% … Chlorine-35
25% … Chlorine-37
Multiply the mass of each isotope by the %...
(.75 x 35) + (.25 x 37) = amu

7. Check
Boron (B) has two naturally occuring isotopes: Boron-10 (abundance = 19.8%, mass = amu) and Boron-11 (abundance =80.2%, mass = amu)
Calculate the atomic weight(mass) of boron.

8. Radioactivity Nuclear Reactions Radioactivity Radiation
Changing of the atom of one element…into the atom of another element
Radioactivity
Spontaneous emitting of radiation
Radiation
Rays and particles...? Will discuss later.
Radioactive Decay
Unstable radioactive atoms decay into stable nonradioactive atoms…often forming different elements

9. α Types of Radiation Alpha Radiation -
Alpha particles = 2protons & 2 neutrons (2+ charge)
Results from alpha decay reaction

10. Equation of alpha ( ) Radiationα
226 Ra 88
222 Rn 86 4 He 2
Radium-226
Radon-222
α particle

11. β Types of Radiation Beta Radiation -
Beta particle= electron with a charge of -1
Conversion of a neutron into a proton
Releases a fast moving electron
Mass # stays the same… Atomic # increases

12. Equation of beta ( ) Radiationβ 14 C 6 14 N 7 β -1
Carbon-14
Nitrogen-14
β particle

13. Types of Radiation Gamma Radiation Gamma Radiation -
High energy radiation
Energy lost due to beta and alpha radiation
Gamma Radiation
gamma ray

14. Equation of gamma ( ) Radiation
238 U 92
234 Th 90 4 He 2 2
Uranium-238
Thorium-234
α particle
particle

15. Review

16. Dangers

17. The Scientists In your note book
Identify the contributions of the following Scientists
Democritus’s Ideas
Aristotle
Dalton’s Atomic Theory