2. Democritus Pneumonic Device Democritus’ Atomos No Slice
440 BC (2,500 years ago)
Hypothesis
ALL matter is made of particles too small to be seen, that cannot be split into smaller parts
“Atomos” meaning “cannot be cut”
Atomic Model
Sugar is made of “sugar atomos”
Rocks are made of “rock atomos”
Copper is made of “copper atomos”

3. John Dalton 1803 Experiment Hypothesis
Measured masses of elements and compounds during chemical reactions
Hypothesis
All elements are made of atoms
All atoms of the same element are IDENTICAL
Compounds contain atoms of more than one element
The same compounds always combine the same way

4. Dalton’s Atomic Model Tiny, solid, indestructible particles
“Bowling Ball Theory”
Pneumonic Device
Dalton’s
Atomic
Bowling
Balls
Solid
Compounds
And
Bowling Balls Of
John Dalton

5. J.J. Thomson 1897 Experiment Hypothesis
Shot lasers between two magnets ( + & -). Laser bent towards the positive magnet.
Hypothesis
Atoms made of smaller particles
Atoms have a neutral charge
Atoms are positively charged “blob” of matter, with little negative charges scattered throughout.

6. J.J. Thomson’s Atomic Model
Tiny solid sphere (like Dalton) but with negative charges scattered throughout
“Plum Pudding”
Think of mint-chocolate chip ice cream
Pneumonic Device
Thomson’s
Unique
Plum Pudding
And
Charges

7. Ernest Rutherford 1911 Experiment Hypothesis
Shot alpha particles (+ charge) at gold foil. The particles bounced off in crazy (unpredicted) directions
Hypothesis
Atoms have very small, positively charged nucleus
Nucleus surrounded by negative charges orbiting nucleus
Atoms are mostly empty space

8. Rutherford's Atomic Model
“Planetary Model”
Negatively charged electrons orbit positively charged nucleus
Mostly empty space
Pneumonic Device

9. Neils Bohr 1913 Experiment Hypothesis None! Just a super smart dude.
Electrons orbit the nucleus at fixed distances.
Each distance is an energy level.
Electrons gain or lose energy as they move between energy levels.

10. - - - - - - - Bohr’s Atomic Model “Bohr Model”
Most commonly used in chemistry and chemistry classes
Pneumonic Device - - - - - -

11. Erwin Schrödinger 1926 Experiment Hypothesis
None! Just a super smart dude.
Hypothesis
Electrons orbit the nucleus in a sort of “cloud”
“Cloud” describes where electrons probably are

12. Schrödinger’s Atomic Model
“Electron Cloud Model”
Most accurate model of the atom
Difficult to use for science problems
Pneumonic Device

13. Let’s make a timeline!
With a partner, get a piece of large construction paper from the front of the room.
NEATLY divide the paper into SIX sections
Using the colored pencils provided (use lots of color!) to draw colored pictures of the evolution of the atomic model.
ABOVE each picture of each model, you must write the name of the scientist who developed the model, the year that they developed it, and important information about what they added to their model and why it is important.
You will be graded on NEATNESS, CREATIVITY, ACCURACY, and EFFORT.

14. Here is a sample… 440 “Atomos”
There is a limit to how small you can make particles
“Bowling Ball Theory”
Atoms and mix to make compounds
“Plum Pudding”
Atoms are positive with negative charges mixed throughout

15. Ch. 4/5 Notes Day 3
1/28/16

16. ATOMS!!!!
Particle
Symbol
Relative Charge
Electron e-
negative
In the Nucleus…
Proton p+
Positive
Neutron n
Neutral n p+ e-
Protons and neutrons take up most of the mass of an atom. The rest is mostly empty space!

17. All of this information is in the Periodic Table
Element Name
Atomic Number – the number of protons that are in the nucleus of one atom of an element. **Also equal to the number of electrons in the element.
Chemical
Symbol
Atomic Mass – the SUM of the number of protons and neutrons that are in the nucleus of one atom of an element.

18. Let’s Practice… Element Name Chemical Symbol # of Protons Element Name
# of Electrons
# of Neutrons
Element Name
Chemical Symbol
# of Protons
# of Electrons
# of Neutrons

19. Maximum number of electrons
Energy Level
Maximum number of electrons 1 2 8 3 18 4 32

20. Draw the following atoms of the elements in your learning log!
Give the atomic #, Atomic Symbol, Atomic mass and number of protons, neutrons and electrons for each element.
Use three different colors to represent the neutrons, protons and electrons.
Oxygen
Carbon
Chlorine
Hydrogen
Argon
1 atom of your choice

21. Isotope
An element that has the SAME number of protons (atomic #) but DIFFERENT number of neutrons.
Elements with the SAME number of protons are the SAME element.
**The atomic Mass on the periodic table is the most common mass of that element. You could think of it as the “average weight” of an element.

22. Example All Oxygen atoms have 8 protons, but can have different numbers of neutrons
16.999
17.999

23. Because scientists are ridiculous…
Here is another important way to write atomic number and atomic mass B 11
Atomic Number 5
Atomic Mass

25. Which of the following “unknown” elements are isotopes of Platinum
194 78
194 77
196 78

26. Which of the following “unknown” elements are isotopes of Tin
120 50
116 50
117 51

27. Which of the following “unknown” elements are isotopes of Antimony
120 50
121 50
123 51