1. Do First
Actions: Get the 4 sheets: Atomic Structure Interactive, Calculating Protons, Neutrons, and Electrons Sheet, Bohr Model worksheet and It’s Natural reading stamped
Questions:
An oxygen atom with an atomic mass of 18, has how many neutrons?
O-2 has how many electrons?

2. Agenda Interactive Simulation (10 minutes) Isotope Notes
Average Atomic Mass Practice 1

3. Interactive Simulation (10 minutes)
Answer the questions using the website on the sheet
If you finish before I call time, then ask me to stamp it
If you finish afterwards, then I will stamp it when we get to practice

4. Isotopes Notes

5. Isotopes
Remember that the MASS NUMBER of an element equals the number of protons PLUS the number of neutrons in its nucleus
If atoms of the same element have different masses, they are said to be ISOTOPES of that element
Isotopes of an element have the same number of protons and electrons, but a different number of neutrons

6. U Naming Isotopes Hyphen Notation Nuclear Symbol Notation
Mass number is written with a hyphen after the name of the element
Ex: Uranium-235
Nuclear Symbol Notation
Superscript indicates mass number
Subscript indicates atomic number
Ex: U
235 92

7. How to find number of Neutrons
The number of neutrons is found by subtracting atomic number from mass number.
Ex:
235 – 92 = 143 neutrons U
235 92

8. Average Atomic Mass
The isotopes of an element contribute to that element’s average atomic mass based on their abundance on earth
In other words, the weighted average of all the carbon isotopes naturally found on earth is
Where does this number come from?

9. Calculating Average Atomic Mass
For each isotope, multiply the mass by the % abundance.
Add answers together to get the average atomic mass
Example
There are two naturally occurring isotopes of copper
69.17% copper-63
30.83% copper-65
( x 63) + ( x 65) = ~63.96 amu

10. Average Grade
Classwork/Homework (10%) 100 Test (50 %) 70 Quiz (25 %) 70 Lab (15 %) 100 What is the above student’s grade?

11. Let’s do the first on each sheet together

12. Practice on Your Own Start on sheet 1
If you don’t get them stamped today, they will turn into homework
Raise your hand if you need help

13. Did You Learn?
1. How many neutrons does the below potassium atom have?
2. How many neutrons does Li – 9 have? K 42 19