Catalyst – September (2+2)(7), 2009 Please pass up COMPLETED Rap Battle Assignment to the first person in the row so I can stamp them. Write a sentence describing what a theory is. Why weren’t cell phones invented when regular phones were? (Weekly Goal should already be completed)

Honors Catalyst – September 5(2 3 -2), 2009 Please pass up COMPLETED LHC articles to the first person in the row so I can stamp them. Write a sentence describing what a theory is. Why weren’t cell phones invented when regular phones were? (Weekly Goal should already be completed)

Today’s Agenda  Catalyst  Go over Homework  Rap Performances?  Atomic Theory Part 1  Work Time  Exit Question  Homework: Hollow Earth article

Today’s Agenda - Honors  Catalyst  Review LHC Article  Atomic Theory Part 1  Work Time  Exit Question  Homework: Hollow Earth Article, think about Science Fair topic and get notebook by Monday!

Today’s Objectives  SWBAT describe the evolution of the atomic theory from 420 B.C. to  SWBAT compare and contrast the contributions of Dalton and Thomson.

What is an atom? Key Point #1: An atom is the smallest part of an element that retains (keeps) the properties of the element

Well then, what is an element? Key Point #2: An element is a pure substance that cannot be broken down into simpler substances by physical or chemical means NOT THIS KIND OF ELEMENT

Well then, what is an element? Key Point #2: An element is a pure substance that cannot be broken down into simpler substances by physical or chemical means NOT THIS KIND OF ELEMENT

Well then, what is an element? THESE KINDS OF ELEMENTS

Why is the atom so important? The atom is the building block of all matter! Without atoms, our universe would no exist!

Essential Questions for Unit 3 1) Who made the most important contribution to the development of atomic theory? 2) What makes one atom different from another? How are they similar? 3) Why is it so important to understand how the periodic table is organized? 4) What secrets can we uncover about the elements using the periodic table?

The Playas of Atomic Theory Democritus ( B.C.) Aristotle ( B.C.) John Dalton (1808) J.J. Thomson (1898) R.A. Millikan (1909) Ernest Rutherford (1909) Niels Bohr (1913) Chadwick (1932)

How in the World Did These Playas Figure All This Out!?!

Numero Uno! - Democritus ( B.C.)  Experiment: Observations and inferences  No REAL experiment…just IDEAS  Where: Greece  When: 420 B.C.  First theory of the atom  The “birth” of the atom Page 88

What were Democritus’ conclusions? Matter is composed of tiny particles called atomos Different kinds of particles have different sizes and shapes Particles move through empty space

Numero Dos! - Aristotle ( B.C.)  Aristotle gave us this quote…  Among other things…  He challenged the ideas of Democritus  He did not think the “nothingness” of empty space could exist “We are what we repeatedly do. Excellence, therefore, is not an act but a habit.” Page 88-89

Numero Tres! - John Dalton ( ) Experiment: Careful chemical measurements Where: England When: 1803 Page 90

Dalton’s Four Postulates 1. All elements are composed (made up) of atoms. It is impossible to divide or destroy an atom. 2. All atoms of the same elements are alike. (Ex: One atom of oxygen is like another atom of oxygen.) Atoms of different elements are different. (Ex: An atom of oxygen is different from an atom of hydrogen.) 3. Atoms of different elements combine to form a compound. 4. Chemical reactions occur when atoms rearrange.

What were Dalton’s conclusions? Atoms are hard, round, solid balls. They are similar to marbles.

Numero Cuatro! - J. J. Thomson ( ) Experiment: Cathode ray tube When: 1898 Where: England

Thomson’s Cathode Ray Tube Quick! Reading Time!  Pages  Stop at “The next significant development….”

Thomson’s Cathode Ray Tube Electrons are NEGATIVE!

So what does this mean about the nature of atoms?  It was known that all matter was neutral (no positive or negative charge)  So if the electron is negative, then what does that mean about the rest of the atom?

He said the atom was a ball with electrons floating around in positive space Atoms can be divided into smaller SUBATOMIC particles! Thomson’s CONCLUSIONS

Wait! Back to Thomson! Now I can finish my model! It looks like Plum Pudding!

Work Time  On your own paper, compare and contrast the theories of Dalton and Thomson  Write at least 1 paragraph (5 sentences or more)  Include picture of each theorist’s model.

Exit Question 1. Why do theories evolve over time? 2. Do you think a theory will ever be completely developed? Why or why not?

Numero Cinco! - R. A. Millikan  Experiment: Millikan Oil Drop Experiment  When: 1909  Where: U.S.A!!!!

Millikan’s Oil Drop Experiment

Millikan’s Calculations – Whoa!

What were Millikan’s conclusions? I have most accurately measured the charge of an electron: x Coulombs

What were Millikan’s conclusions? I have also most accurately measured the mass of an electron: x kg

Numero Seis! - Ernest Rutherford  Experiment: Gold Foil Experiment  When: 1910  Where: Montreal

Gold Foil Experiment Explained  Alpha helium particles were shot through a piece of gold foil  Think aluminum foil but thinner and made out of gold!  Alpha helium particles are 8000 times more massive (bigger) than electrons, so Rutherford thought they would knock electrons out of the way, but they did not!

Remember! This is the current model of the atom (Thanks to Thomson)

More History Ernie’s (Rutherford) Big Adventure Thin Sheet of Gold Atoms

What were Rutherford’s conclusions?  Pretend you are Rutherford  As Rutherford, what conclusion would you make based on the data from the Gold Foil Experiment? = Hint: Positive repels positive, negative repels negative

What were Rutherford’s conclusions?  The deflected alpha particles were hitting something with a concentrated mass and positive charge  Discovered and named the nucleus

Rutherford’s Conclusion  Atoms are made of mostly EMPTY SPACE!  Actually, the ratio of the size of the nucleus to the diameter of the orbits of electrons can be compared with placing a marble in the middle of a football stadium!

Empty Space Continued  “Neutrons and protons occupy the atom's nucleus. The nucleus of an atom is tiny -- only one-millionth of a billionth of the full volume of the atom -- but fantastically dense, since it contains virtually all the atom's mass. As Cropper has put it, if an atom were expanded to the size of a cathedral, the nucleus would be only about the size of a fly -- but a fly many times heavier than the cathedral.” -A Short History of Nearly Everything by Bill Bryson

James Chadwick  Experiment – Beryllium Foil Experiment  When  Where – Cambridge Conclusions – Neutral radiation emitted; therefore, the nucleus contains another subatomic particle called the neutron (has a neutral charge)

Atomic Parts  Electron - subatomic particle with a 1- (negative) charge  Nucleus – tiny, dense region in the center of an atom that has a positive charge and contains most of the atom’s mass  Proton – a subatomic particle that has a 1+ (positive) charge  Neutron – a subatomic particle with neutral (or no) charge

NUCLEUS NEUTRON ELECTRON PROTON

Compare and Contrast What are the similarities and differences between each contribution? How did each theorist add to or reject the discoveries or ideas developed before him?

RAFT - Independent Work Time R = Role Pretend to be either Dalton or Thomson. A = Audience You are writing to inform everyone of your discoveries! F = Format Letter, Newspaper column, or Rap T = Topic Details of your discovery and how you know it is true - YOU HAVE “WORKED” HARD…DEFEND YOUR RESEARCH!

Exit Ticket 1. Can people think that theories are correct even when they are not? How does this happen? How is it that theories change? 2. What was Dalton’s biggest contribution to atomic theory?

Assignment: RAFT  Option 1: Rap  Role: An atomic Theorist  Audience: Writing to another atomic theorist  Form: an appropriate rap  Topic: Why your theory and model is better than theirs +3 points for presenting on Monday

Assignment: RAFT  Option 2: Polite, Formal Letter  Role: An atomic Theorist  Audience: Writing to another atomic theorist  Form: a formal letter  Topic: Politely stating why your theory and model proves theirs wrong +3 points for presenting on Monday

Assignment: RAFT Things to Include  Personal information about both theorists - where they’re from, physical appearance, etc.  All necessary facts about both theories or models  How the theory is better than the one that came before it

Exit Question

Atomic Number Element Symbol Atomic Mass