1. DO NOW
Object A at 40ºC and Object B at 80ºC are placed in contact with each other. Which statement describes the heat flow between the objects?
Heat flows from object A to object B.
Heat flows from object B to object A.
Heat flows in both directions between the objects.
No heat flow occurs between the objects.

2. Introduction to Atomic Theory
Williamsburg High School for Architecture and Design
Mr. Quinn and Ms. Tom
9/17/13

3. AIM: What are atoms made of?
What Do We Already Know?

4. Origins of Atomic Theory
AIM: What are atoms made of?
Origins of Atomic Theory
Atomic theory was developed by John Dalton in the mid 1800s
He used a combination of laws from chemical reactions

5. Origins of Atomic Theory
AIM: What are atoms made of?
Origins of Atomic Theory
J. J. Thompson developed the first model of the atom
Developed from cathode ray tubes
“Plum pudding model:” a positive cloud with negative particles in it

6. Origins of Atomic Theory
AIM: What are atoms made of?
Origins of Atomic Theory
Rutherford came up with the next model of the atom
Gold foil experiment
Atoms are mostly empty space

7. Origins of Atomic Theory
AIM: What are atoms made of?
Origins of Atomic Theory

8. Parts of the Atom Particle Mass Charge Proton 1 +1 Neutron Electron -1
AIM: What are atoms made of?
Parts of the Atom
Particle
Mass
Charge
Proton 1 +1
Neutron
Electron -1

9. AIM: What are atoms made of?
WAIT! Are you ready?

10. Exploring Atomic Theory
AIM: What are atoms made of?
Exploring Atomic Theory
Atoms start with a charge of zero. What does that mean for the number of protons and electrons in an atom?
They are the same!
Each element is identified by a unique atomic number. The atomic number is equal to the number of protons. What is the relationship between the atomic number and the number of electrons?

11. Exploring Atomic Theory
AIM: What are atoms made of?
Exploring Atomic Theory
Do positive and negative charges attract or repel each other?
Electrons orbit the nucleus like the earth orbits the sun. Why doesn’t the earth fall into the sun?
Electrons don’t fall into the nucleus for the same reason
They are orbiting too quickly

12. Exploring Atomic Theory
AIM: What are atoms made of?
Exploring Atomic Theory
The other number in each box on the periodic table is the atomic mass. For the small elements, what do you notice about its relationship to the atomic number?
It is about double
If the atomic number is set and electrons don’t have a mass, what makes up the balance?
Neutrons
What is the relationship between the number of protons and neutrons for most elements?
They are about equal

13. Exploring Atomic Theory
AIM: What are atoms made of?
Exploring Atomic Theory
Do similar charges attract or repel each other?
Repel
So would a bunch of protons in the nucleus attract or repel each other?
It is neutrons that hold them together.

14. AIM: What are atoms made of?
WAIT! Are you ready?

15. Problem #1 The mass of a proton is approximately equal to the mass of
AIM: What are atoms made of?
Problem #1
The mass of a proton is approximately equal to the mass of
an alpha particle
an electron
a neutron
a positron

16. AIM: What are atoms made of?
Problem #2
What is the mass number of a carbon atom that contains six protons, eight neutrons, and six electrons? 6 8 14 20

17. AIM: What are atoms made of?
Problem #3
Which two particles make up most of the mass of a hydrogen-2 atom?
electron and neutron
electron and proton
proton and neutron
proton and positron

18. AIM: What are atoms made of?
Problem #4
Which statement about one atom of an element identifies the element?
The atom has 1 proton.
The atom has 2 neutrons.
The sum of the number of protons and neutrons in the atom is 3.
The difference between the number of neutrons and protons in the atom is 1.

19. Problem #5 What is the charge of the nucleus of an oxygen atom? –2 +8
AIM: What are atoms made of?
Problem #5
What is the charge of the nucleus of an oxygen atom? –2 +8
+16