1. Pudding and clouds
Atomic Models

2. Pudding and Clouds Chem Catalyst:
In the 5th century a Greek philosopher named Leucippus and his student, Democritus, said, “ All matter is made up of particles called atoms.”
Do you think atoms are composed of smaller pieces?
If there are smaller pieces of an atom , how would they differ from each other?

3. Connections to the past
On the cards used in “Create a Table”:
What do you think the size of the circle represents?
What do you think the pegs or sticks represent?

4. Atoms
Atoms are extremely small particles, which cannot be seen with the eye or regular school microscopes
An atom is the smallest amount of a element that can exist and still have the properties of that element
All matter is made up of atoms.

5. Charge Fundamental property of atom and their parts
Related to the forces pushing or pulling the atom pieces
A piece can have positive, negative or neutral charge

6. For most of time
People were talking about atoms without having ever actually seen any picture of one.
They came up with visual and descriptive representations of concept of an atom, called a model or theory

7. Atomic model
Atomic model or theory represent the best explanation for the design and workings of an atom by a specific person or group, based on the scientific evidence available
As new evidence is gathered, models are refined and changed.

8. Theories and models are not casual ideas
Not proposed without testing, and research
Then it is tested repeatedly by the scientific community
It is valid until contrary evidence is found, then modified or discarded.

9. The Big Question
How have chemists thought about the atom through history?
Unit 1 • Investigation III

10. Goal of the section
By the completion of the section you should be able to:
Identify the major components of any atom
Use the concepts of the latest theory on atomic structure to explain how a atom is set up and operates
Understand the 5 major versions of atomic theory and be able to compare and contrast them

11. Activity
Purpose: This lesson will introduce you to various models for the atom that have appeared over the past two hundred years. The descriptions of five models of the atom are on a separate handout.
(cont.)
Unit 1 • Investigation III

12. Part 1 Organize the models in chronological order
Based on information listed on the cards, organize the models in chronological order.
In comp book List models A thru E from earliest model to current model. Explain what evidence you used to arrange models

13. Part 2: Organizing Models and evidence by Year and Name
A 2nd set of handouts will be given to students.
Use 2nd handout set to determine if your original chronological order of models was correct.
In Comp book, create and complete a chart with the following information

14. Does
Model
Indicate
Existence
of:
Model Name
People behind model concept
Electron
Proton
Neutrons
Nucleus
Electrons moving in paths or orbits
Electrons moving randomly
Billiard
Ball
Plum
Pudding
Nuclear
Solar
System
Current

15. Part 3: Matching evidence with Models
Each pair of students will then be given 6 pieces of evidence about atoms.
For each piece of evidence, compare the information of 2 models to determine which model supports or agrees with the piece of evidence the best. Explain your answer in your composition book

16. (cont.)
Five Models of the Atom
Unit 1 • Investigation III

17. Five authors and their big ideas
John Dalton Atom as a solid sphere, Different atom for each element
JJ Thompson Electrons
Ernest Rutherford Nucleus
Niels Bohr Electron Orbitals/Shells
Protons
Heisenberg,Chadwick Electron Cloud / Neutron

18. Acting out the models

19. Alpha particles
Helium nucleus stripped of its electrons

20. Current Model
Every atom is composed of a tiny, dense, positively charged nucleus located at center of atom. Nucleus is composed of positively charges protons and neutrally charged neutrons
Mass of a proton and neutron are the same
Electron Cloud: region of atom around the nucleus occupied by fast moving, almost mass-less, negatively charged electrons.
An atom (and electron cloud) is made up mostly of space, almost all mass of atom is located in the nucleus
Electrons do not all move at the same distance from the nucleus. Some are closer or farther away ,depending on amount of KE they possess
Paths of electrons are not orbits like planets, but more randomized. It is impossible to predict the exact location of an electron at a point of time.

21. Electron
Proton
Neutron
Nucleus
Charge
Mass
Location

22. Part 4 In comp book, write Definitions for: Proton Neutron Electron
Nucleus
Electron Cloud, orbit, shell
Void

23. Difference between clouds, orbits and shells
Electron cloud: Includes all space in an atom outside of a nucleus where an electron may be found, mostly void
Electron Orbit: 2 Dimension representation of an electron’s position based on the amount of KE energy it possesses
Electron Shell: 3 dimensional representation of a electron orbit

24. Notes (cont.)
Unit 1 • Investigation III

25. Wrap-Up
All matter is made up of extremely small particles called atoms. These particles are too small to be seen even with a regular microscope.
Science is theoretical and dynamic. Models and theories are continually being revised, refined, or replaced with new models and theories.
Unit 1 • Investigation III

26. Check in Does a nucleus have a positive, negative or neutral charge
Which has more mass?
A proton from a Helium atom
An electron from a Helium atom
A neutron from a Helium atom
A nucleus from a helium atom
An alpha particle

27. Check in
#3 Match the Scientist’s name to the Model Name below to which he is associated. Organize from oldest (1) to most recent (5)
Chadwick Plum Pudding
Bohr Solar System
Dalton Current Model
Thomson Billiard Ball
Heisenberg Nucleus
Rutherford