...Bohr's Model

Bohr theory is the most well known and used.
-Electrons exist in orbitals
-when they absorb energy they move to a higher orbital
-as they fall from a higher orbital to a lower one they release energy as a photon of light
-atoms are electrically neutral
-two different models can be used to describe electron configuration
  -energy level model
  -Bohr model

...Atomic Theory

The atom has had many different interpretations in the past, many of which have been proven wrong. Scientists over the years have corrected and worked on these ideas into a theory that we use today.


Four Element Theory  
-first theory of matter
-everything was made in part of water, wind, earth, fire.
(not a scientific theory because it could not be tested)


Democritus(300BC) 
-the first person to have interpreted the atom(atmos).
-Atoms were invisible
(not a testable theory, only a conceptual model)


Lavoisier(late 1700s)
-law of conservation of mass
-law of definite proportions
  water is always 11%(H) and 89%(O)


Proust(1799)
-if a compound is broken down into it's constituents, the products exist in the same ratio as in the compound.
-experimentally proved Lavoisier Laws


Dalton(early 1800s)
-atoms are solid, indestructible spheres (like Billiard balls)
-provides for different elements (these would be different spheres)
-based on the law of conservation of mass 


J.J Thomson(1850s)
-raisin Bun model
(solid, positive spheres, with negative particles embedded in them.)
-first atomic theory to have positive and negative charges
-demonstrated the existence of electrons using a cathode ray tube


Rutherford(1905)
-showed that atoms have a positive, dense center with electrons outside it.
-resulted in planetary model
-suggests atoms are mostly empty space


Bohr model(1920s)
-matter emits light when it is heated
-light travels  as photons
-the energy photons carry depends on their wavelengths


 

...Density and Graphing (10.03.10)

Today we learned about density. The density of an object is it's mass divided by it's volume.(Density=Mass/Volume) It's usually expressed in kg/L, kg/m3, or g/m3.

Example: in order to determine the density of a statue with a mass of 135kg and a volume of 65L all you have to do is divide its mass (135kg) by its volume (65L)
D=m/v
D=135kg/65L
D=2.1kg/L


We also learned about graphing.
All graphs must contain five things:
1)Labeled axis
2)Appropriate scale
3)Title
4)Data points
5)Line of best fit (usually straight)


Three things can be done when working with a graph:
1)Read the graph
2)Find the slope(rise/run)
3)Find the area under the graph