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Chemistry 11
Assignment on Early Atomic Models
Name ___________________________
Date ____________________________
Due Date ________________________
Mark ________/10
Chemistry 11
Assignment on Early Atomic Models
Log on to the SSS Chemistry Website at http://sd67.bc.ca/teachers/dcolgur Click
“Chemistry 11” and scroll down to “Unit 8”
Also have your Student Workbook open to page 139 to start this worksheet.
Click “The Necklace of Democritus” in the “Other Links” Column on the right of the
Chem. 11 Web page
1.
Who first came up with the idea of indivisible particles or “atoms” in the 5th Century in
Greece? ___________________. The student of his who further developed the idea was
__________________________.
2.
Now, click the “back” button and click the link called “Dalton’s Atomic Theory”.
When did John Dalton propose his atomic theory? ___________
List the 4 main ideas in Dalton’s Atomic Theory.
1)
2)
3)
4)
Are all these ideas still regarded as correct? _____________
3.
Now, click “back” and click the site called “J.J. Thomson and his Experiments” Scroll
down a bit and click “Enter the Exhibit”.
The green glow in electrically charged tubes was known as ______________ rays.
Thomson speculated that these rays were composed of little particles smaller than the atom.
He first called these particles ____________________________.
What did the discovery of these particles suggest about Dalton’s “indestructible atoms”?
Later on, the little particles composing cathode rays were found to be very light and have a
negative charge. They were called _____________________________.
Assignment on Early Atomic Models
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Chemistry 11
Assignment on Early Atomic Models
4.
See the picture of Thomson’s model on p. 141 of SW (Student Workbook). It consisted of a
________________ of _____________ charge with electrons (negative charges) distributed
throughout the ball. It was nicknamed the _____________________ model.
Make a sketch of it here:
5.
In 1909, the mass of the electron was shown to be about _____________________ g.
6.
Now, go back to the Chem. 11 Web page and click the site called “Applet on
Rutherford’s scattering experiment”
Scroll down a little and answer the following questions:
__________________ particles were “fired” at a thin sheet of __________ foil. A zinc
sulphide screen is placed next to the foil. Geiger and Marsden expected to find that
most of the alpha particles travel _________________________________________
with little deviation. This thinking was based on the theory that positive and negative
charges were ____________________________________ within the atom, as was
suggested by Thomson.
Now, scroll back up a little to the animation. Click the little “slider” under the
Slit Width” and hold the mouse button down. Try moving the slider slowly to the right
to open up the slit wider. Open it up to about 3 nm. What happens to some of the alpha
particles now? _________________________________________________. Open the
slit even wider. Most particles pass straight through, but some are _______________.
What are these particles hitting to make them deflect? _________________________.
7.
Thus Rutherford and his co-workers discovered that atoms contained a tiny solid core
called the _____________________________. Where were the electrons in
Rutherford’s model? ___________________________________________________.
What was between the electrons in the area outside the nucleus? ________________
8.
Now, hit the “Back” button until you get back to the Website. Click the link called
“Explanation of Spectra and Bohr Model”. Start reading at “Spectral Lines”. Keep reading
until it says “Pick an element from the menu to see its spectral signature." What you see
now is the spectrum of white light from an incandescent light bulb. Click the arrow by the
little box that says, “white light” until you get the spectrum of hydrogen. How many
coloured lines can you see clearly? _________________. What colours are they? _______
________________________________. Scroll down to sodium and look at it’s spectrum.
Which line on sodium’s spectrum is the brightest? _______________________. What
colour are sodium vapor lights seen in some parking lots and streetlights? ____________.
9.
Scroll down to the bottom of the page. The Danish physicist ___________________ came
up with the answer to explain why spectra of elements were lines of only certain colours.
Click the “Next” box. What “rule” did electrons have to follow? __________________
______________________________________________________________________
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Chemistry 11
Assignment on Early Atomic Models
10. Scroll down a bit and play with the little model. Click on the dotted lines which represent
the allowable orbits for the electrons. Click on orbits and make the
electron move up and down. Scroll down a bit in the explanation.
The little squiggly lines that push the electron up or are released
when the electron jumps back down are called _____________. Are
they all the same colour? ________________. The same
wavelength?____________________. The energy changes of the
little allowable “jumps” are called _______________________.
11. Scroll down and click the “Next” button. Did scientists keep the model of electrons flying
around in little circles? _____________________. Instead of “orbits”, scientists use the
term, “energy ______________”.
12. Now, scroll down further until you come to the atomic model again. This time when you
click on different orbits, notice the arrows on the “energy level diagram” on the left. The
energy level diagrams are what scientists use to keep track of the
electron. A bigger jump results in a _________________ arrow.
13. Now to see how Bohr’s model explains the spectrum of hydrogen, scroll down and hit the
“Next” button. Transitions between the same energy levels always produces the same
___________ photon. Scroll down and play with the next model. Notice how a “line” forms
on the spectrum when an electron jumps down. Different jumps give different ___________
on the spectrum. These different lines appear as different coloured lines on the actual
hydrogen spectrum.
14. Now, go back to the “Chemistry 11” web page and click on the “Short Bio on Neils Bohr”
Bohr was born and educated in _______________________________. He studied
__________________ and played ____________________________. What was the main
problem with Rutherford’s model of the atom? _________________________________
____________________________________________________________________.
According to Bohr’s theory, electrons existed at ___________ levels of energy, that is, at
________________ distances from the nucleus. If the atom absorbed energy, the electron
jumped to a level ____________ __________ the nucleus; if it radiated energy, it fell to a
level ______________ ____ the nucleus. He received the _________________________
for this work in ________________. In 1939 Bohr visited the United States with the news
from Lise Meitner (who had escaped German-occupied Austria) that German scientists were
working on splitting the atom. This spurred the United States to launch the
____________________________________ to develop the ___________________. What
is the name given to element 109? ________________________. Element 107?
___________________. Bohr went on to organize the ___________________________
Conference in Geneva in _________________________________.
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