1. Warmup 11/10/15
Which of the following statements about density is true?
Density depends on mass and volume.
Density is weight per unit volume.
Density is measured in milliliters.
Density is a chemical property.
Which change of state is exothermic?
Sublimation
Melting
Condensation
Freezing

2. 12.1 Atomic theory

3. Close reading First Read Through Look at pictures only.
What do you think the pictures represent?
Second Read Through
Only skim and highlight all of the names you find.

4. Atomic Theory
A scientific theory is a unifying explanation for a broad range of hypothesis and observations supported by testing.
Democritus proposed the first “uncuttable” particle.
Called atom from Greek atomos meaning indivisble.

5. Image taken from: www.ldeo.columbia.edu/.../v1001/geotime2.html
Antoine Lavoisier
Known as the “Father of Modern Chemistry”
Was the first person to generate a list of thirty-three elements in his textbook.
Devised the metric system.
Was married to a 13-year old Marie-Anne Pierette Paulze; she assisted him with much of his work
Image taken from:

6. John Dalton In 1803, proposed an Atomic Theory which states:
1. All substances are made of atoms;
2. Atoms of the same element are exactly alike, and atoms of different elements are different
3. Atoms join with other atoms to make new substances
Calculated the atomic weights of many various elements

7. Close reading Third Read through
Read first two paragraphs aloud to your partner. One paragraph each.
Underline or bracket the main idea in each paragraph.

8. Image taken from: www.wired.com/.../news/2008/04/dayintech_0430
J.J. Thomson
Proved that an atom can be divided into smaller parts
While experimenting with cathode-ray tubes, discovered corpuscles, which were later called electrons.
Stated that the atom is neutral
In 1897, proposed the Plum Pudding Model.
Image taken from:

9. Ernest Rutherford
In 1909, performed the Gold Foil Experiment and suggested the following characteristics of the atom:
It consists of a small core, or nucleus, that contains most of the mass of the atom
This nucleus is made up of particles called protons, which have a positive charge
The protons are surrounded by negatively charged electrons, but most of the atom is actually empty space
Image taken from:

10. NielS Bohr This model was introduced in 1913
Proposed that electrons move in set paths around the nucleus.
These levels are a set distance from the nucleus
Electrons can jump levels but not stay between.
NOTE: It is inaccurate but still widely used as a basis for understanding.

11. Draw this nitrogen atom

12. Modern Theory
Many scientists have since added to the theory and model of the atom.
Schrödinger and Heisenberg discovered that the path is not exact and can only be predicted.
Electron clouds are the regions inside an atom where electrons are likely to be found.

13. James Chadwick
Realized that the atomic mass of most elements was double the number of protons → discovery of the neutron in 1932
Worked on the Manhattan Project
Worked with Ernest Rutherford
Won a Nobel Prize

14. History of the Atom - Timeline
Antoine Lavoisier
makes a substantial number of contributions to the field of Chemistry
J.J. Thomson discovers the electron and proposes the Plum Pudding Model in 1897
Niels Bohr proposes the Bohr Model in 1913
James Chadwick discovered the neutron in 1932
1766 – 1844
1871 – 1937
1887 – 1961
460 – 370 BC
1700s
1800s
1900s
Erwin Schrodinger describes the electron cloud in 1926
Democritus proposes
the 1st atomic theory
John Dalton proposes his atomic theory in 1803
Ernest Rutherford performs the Gold Foil Experiment in 1909
1891 – 1974
1743 – 1794
1885 – 1962
1856 – 1940
Click on picture for more information

15. Democritus & John Dalton+ -
The structure of an atom, according to:
Democritus & John Dalton
James Chadwick
J.J. Thomson
Neils Bohr
Ernest Rutherford
Erwin Schrodinger

16. Review In what part of the atoms is most of the mass located?
What are two differences between the atomic theory described by Thomson and that described by Rutherford?
Identify the difference in how Bohr’s theory and the modern theory describe the location of electrons.

17. Warmup Which of the following determines the identity of an atom?
Atomic number
Mass number
Atomic mass
Overall charge
How many protons does an atom of Iron (Fe) have?
55.8 9 26
Unknown

18. Warmup 11/5/14 In what part of the atom is most of the mass located?
Electron cloud
Electrons
Neutrons
Nucleus
Electrons have a __________ charge.
Positive
Negative
Neutral
Infinite