1. Element properties & isotopes
Everett

2. Atomic Number
The number of protons of each atom of that element

3. Identify Atomic Numbers

4. Isotopes Atoms of the same element that have different masses
Different number of neutrons in the nucleus
Same basic chemical behavior
Most elements are a mixture of isotopes

5. Isotopes Nuclide = a specific isotope of an element Example: Hydrogen
Protium is the most common = %
Hydrogen’s atomic mass = amu
Amu=1/12 the mass of one atom
of C-12

6. Mass Number The total number of protons and neutrons of an isotope
Carbon has isotopes with:
6 neutrons
7 neutrons
8 neutrons
Isotopes are identified by
their mass number.

7. Designating Isotopes Two formats for identifying isotopes:
Hyphen notation - Mass number written next to element name or symbol
Hydrogen-3
Uranium-235
Nuclear symbol – mass # over atomic number next to symbol U
The number of neutrons can be found by subtracting:
mass # - atomic number = number of neutrons
235 92

8. Identify Mass Numbers
Argon-30
Iodine-108
Lead-204
Hg F O O

10. Sample Problem #1 Solution:
How many protons, electrons, and neutrons are in an atom of chlorine-37?
Known: name and mass number
Unknown: number of protons, electrons, and neutrons
Solution:
atomic number = # of protons = # of electrons
mass number = # of neutrons + # of protons
Chlorine’s atomic number =

11. Sample Problem #2
How many protons, neutrons, and electrons are in an atom of Platinum-192?
Known:
Unknown:
Solution:

12. Sample Problem #3
How many protons, neutrons, and electrons in an atom of 24P 15
Known:
Unknown:
Solution:

13. Radiation Drawing
Alpha Decay
Beta Decay
Gamma Decay

14. Average Atomic Masses of Elements
Most elements are a mixture of isotopes
Average atomic mass = weighted average of atomic masses of naturally occurring isotopes of an element
Depends on mass and relative abundance of isotopes
Makes it possible to know how many atoms of an element are present in a sample with a measureable mass

15. Calculating Averages 1. Weigh each one and divide by total number
2. Weigh one of each type and average them
3. Find average mass of each, multiply by abundance, and add totals together