1. Warm Up
Silicon (Si) has 14 protons how many electrons are in Si?
What was the outcome of the gold foil experiment?
Which subatomic particles are in the nucleus?
4. Thompson is responsible for finding _____
Argon (Ar) has 18 protons and 22 neutrons. What is Ar’s mass?
Thompson is responsible for finding ______
Which number is always unique to an element
Agenda
Go over Unit 1 Test
Notes Unit 2-3
Penny Alchemy lab
Homework
Element Poster and WS
Lab penny

2. Unit 1 Test
According to the scientific method, the variable that you change and manipulate is called
Dependent variable
Independent variable
Which characteristics describes only a compound but not a mixture?
Two or more things are combined
The element ratio is fixed
Substances are combined and mixed
Substances can separated by physical properties

3. Unit 1 Test

4. Unit 1 Test
Water to steam is physical change because H2O remain the same in both phases
Baking soda and vinegar is a chemical change because it creates CO2 gas which is a new compound
Object A = 47 g
Object B = 31.2 g

5. Unit 2-3 Atomic Number and Mass Number
Average Atomic Mass (always the bigger #)
The average atomic mass is different from the mass number

6. Atomic Number and Mass Number
The atomic number is the number assigned to a specific element = # of proton
Unique for each element
Same atomic number = same element

7. Atomic Number and Mass Number
Protons and neutrons account for most of the mass of the atom.
Masses of subatomic particles have units of amu (atomic mass units) because they are too small to use grams.
1 proton = 1 amu
1 neutron = 1 amu
1 electron = ~ amu (doesn’t account for an atom’s mass)
Mass number = # of protons + # of neutrons

8. Check in Find the # of proton, electron and neutron for Beryllium
bill nye atoms

9. Isotopes
Isotopes are atoms of the same element that have different numbers of neutrons.
Because the number of neutrons is different, the mass number will be different too.
The number of protons stays the same!

10. Isotope Symbols
Chemists use a special isotope notation to symbolize an isotope.
2. Isotopes are referred to by their mass number through hyphen notation
Examples: carbon-12 or chlorine-37

11. Average Atomic Mass and Mass Number
The average atomic mass is the average of the mass numbers of all the isotopes of that element.
This picture shows that Molybdenum probably has more isotopes with a mass number of 96, rather than 95, because the average atomic mass is closer to 96.

12. Average Atomic Mass and Mass Number
What is the average mass of Lead? Based on the given stable isotopes
Name of Atom
Mass Number
Abudance %
Lead-204
204
1.4
Lead-206
206
24.1
Lead-207
207
22.1
Lead-208
208
52.4

13. Isotope Symbols Check in
What is the mass of Gold?
How many electron, proton &
Neutron is in Gold?
3. Find the atomic # and mass for Lead-208
4. Find the atomic # and mass for Lead-205

14. Isotope Symbols Check-In
Write out the isotope symbols for:
Chlorine-37
Bromine-81
Uranium-235

15. Penny Alchemy Lab Clean your pennies in vinegar about 30-60 secs.
Place your pennies in the beaker with NaOH and place the beaker on the hot plate
DO NOT BOIL your NaOH solution (bad for lungs)
Do not overlap your pennies
Wait until your penny completely turned silver before taking it out of your NaOH solution
If you don’t have a penny see me and bring $$$ joke

16. Assignments Element Poster Lab penny
Worksheet (front side of the poster)