Good Day! 04/20/23Starter: What does an atom look like?

Today we will…

Look at grade sheets and discover the history of the atom.

• Goal:

– determine what you do and do not know about atoms

– think about why you believe what you believe

– Gain some understanding on how we came to our current thinking on the atom.

What is an atom?

Why do you believe that they exist and everything is made out

of them?

Tear off a piece of paper and rip it in half.

• Now tear it in half again• Now again• Will there come a time where you can’t rip it

in half?• Let’s say you had a shrink ray and could

make yourself smaller so the size of your hands was not an issue.

• Could you then?• Numbers can be “cut” in half forever, why

not paper?

We are not the first to struggle with this concept

• In ancient Greece (400 B.C) a man named Democritus came up with the idea that you will eventually come to a point where you can no longer cut an object in half

• He said you would come to an “uncuttable” object.

• Brain Pop

A choice

• I am about to hand out a worksheet

• You can either work on it by yourself and receive 15/15 if you complete it. Or you can watch a video and powerpoint and get 12/15 if you complete it.

• The choice is yours

• Brain Pop

Atomic Theory and Models

Dalton thought that

• atoms were like smooth, hard spheres that could not be broken into smaller pieces.

• All atoms of an element were identical

• An atom of one element can not be changed into an atom of a different element.

Atomic Theory and Models• Thomson suggested

that atoms had negatively charged electrons embedded in a positive sphere.

• We had to revise our model of the atom because the negative charges had to be balanced by a postive charges to keep the atom neutral.

Rutherford found that most particles went through proving that atoms (and everything made of them) are mostly empty space.

• Rutherford was surprised that a few particles were deflected strongly. This led him to propose an atomic model with a positively charged nucleus.

Close

up of

What

Happened

inside the

gold foil.

Atomic Theory and Models

• Rutherford’s model looked like what you see here with a positively charged nucleus.

• Bohr figured out that there are levels and developed the Bohr Model

• We coupled this with knowledge that you can’t predict where the electrons will be.

• Chadwick’s discovery of the Neutron lead to a reengineering of the nucleus.

Models of Atoms• A summary of visuals

Video

Want to build an atom?

• Atom builder one

• Atom builder two