BOHR'S MODEL: October 15, 2010

Now that you know the history of atomic theory, let's move on to the more modern stuff, such as Bohr's atomic model!

BOHR (1920S)

• Rutherford's model was inherently usable (protons and electrons should attract to eachother, no?)
• Matter emits light when it is heated (black body radiation)
• Light travels as photons
• The engerdy photons carry depend on their wave length
• Bohr based his model on the engery (light) emitted by different atoms
• - Each atom has a specific spectra of light
• To explain this emission spectra, Bohr suggested that electrons occupy shells or orbitals

Summerizing Bohr's Theory

• 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

Hmm...

When electrons move from level to level (depending on the energy), they don't travel there, they actually just appear there, you could call it "transporting".

This led to us learning (by questioning Mr.Doktor) that scientists have tried harnessing this power to transport more than just an electron. Too bad the most they've ever managed to transport was about 5 atoms...

Still, we never know what lies in the future! Maybe one day we will all quit walking and physical activity and just transport everywhere we go!

Borh-d? (Get it?...Haha.)

Check out

http://phet.colorado.edu/en/simulation/hydrogen-atom

to play around with a hydrogen atom and see many of the different atomic models!

Post by Adrienne Ross

ATOMIC THEORY: October 13, 2010

A timeline, and history, on the modern atomic theory...

ARISTOTLE

• Created the four elements theory
• Lasted about 2000 years
• Believed all matter was formed from 4 basic elements: fire, water, air, earth, which created/connected to make: hot, cold, wet, dry
• It is not a scientific theory because it could not be tested against observation

  

DEMOCRITUS (400-300 B.C.)

• Said atoms were invisible particles
• First mentioned atoms
• Not a testable theory, only a conceptual model
• No mention of any atomic nucleus or its constituents
• Cannot be used to explain chemical reactions

LAVOISIER (LATE 1700S)

• Law of conservation of mass
• Law of definited proportions; example: in a molecule of water (H2O), it will always be 11% H and 89% O, no matter how much or how little water there is

PROUST (1799)

• If a compound is broken down into its constituents, the product exists in the same ratio as the compound
• Experimentally proved Lavoisiers' Laws

DALTON (EARLY 1800S)

• Atoms are solid, indestructable spheres (like billiard balls)
• Provides for different elements (those would be different spheres)
• Based on law of conservation of mass
• Having a molecule (atoms combined in simple whole # ratios) explains the law of constant composition
• If the atoms are not destroyed then the mass does not change

J.J. THOMSON (1850S) 

• Raisin bun model
• Solid, positive spheres with negative particles embedded in them
• First atomic theory to have positive (protons) and negative (electrons) charges
• Demomstrated 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
• Explains why electrons spin around nucleus

Post by Adrienne Ross

to be continued...

TEST DAY!: October 8, 2010

Today we had our Chemistry Unit test. Hopefully we did alright!

REVIEW: October 6, 2010

Today we were suppose to have a Chemistry test but Mr. Doktor is so cool that he postponed it to Friday! Instead of taking a difficult, back breaking chemistry test, we reviewed how to balance chemical equations, ionic formulas, physical and chemical changes, measurement, uncertainty, significant digits, and dimension conversions.

Mr. Doktor also told us to memorize the basic Common Metric Prefixes Used in Chemistry (i.e mega, kilo, deci)

In conclusion, we are ready for our test.........!