Atomic Theory / History of the Atom



Atomic Theory / History of the Atom

Computer Lab

Part 1: Follow the instructions to complete each set of questions using the power point, your book and the websites linked in the power point. In some instances, you will have to view an animation or picture from a website to answer the following questions.

History of the Atom

Timeline of Contributors to the modern atomic theory.

1. List the 12 main contributors to atomic theory in order of the timeline from the power-point. Include the year of their work and the main contribution to the theory.

|Contributor |Year of their Work |Describe briefly their contribution |

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2. Greek philosophers. (click on the link Democritus)

a. Who was responsible for the concept of atoms?

b. Who believed that all substances came from combinations of fire, air, earth and water?

c. Why is Democritus’s view of matter considered only an idea?

d. What does the word “atom” mean?

e. What is the word origin for “atom?”

3. Foundations of Atomic Theory: Dalton’s Components to Atomic Theory

a. List the 4 components to Dalton’s Atomic Theory

b. State two principles from Dalton’s theory that have been revised as new information has become available and explain how this is different from Dalton’s original postulates.

c. Laws that arose from Dalton’s Atomic Theory:

i. Law of Conservation of Matter: matter is neither _________ or ___________. ( only rearranged)

Based on this law, use the following

[pic]

According to the law of conservation of mass, how much zinc was present in the zinc carbonate?

Show your work here and explain how you determined the answer.

ii. Law of Definite proportions or Law of definite composition: a chemical compound always contains exactly the same proportion of elements by mass.

EX.

| H2O, will always have the same percent by weight, 11.2% H  and 88.8% O. |

| |

|H2O = 18.02 g |

|2.02 g H x 100 = 11.2%H & 16 g O x100 = 88.8% O |

|18.02 |

Sample problem: 84.01 g of baking soda, NaHCO3, ALWAYS contains 22.99 g of sodium, 1.01 g of hydrogen, 12.01 g of carbon, and 48 g of oxygen. What percentage of each of these elements is present in baking soda?

a. sodium __________

b. hydrogen ________

c. carbon __________

d. oxygen __________

iii. Law of Multiple Proportions: Elements combine in certain ratios. The same elements can be found in compounds and the difference in ratios gives them very different properties. Ex. H20 vs H2O2

When two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.

EX. In 100 g of the first compound (100 is chosen to make calculations easier) there are 57.1 g O and 42.9 g C. The mass of O per gram C is: 57.1 g O / 42.9 g C = 1.33 g O per g C

In the 100 g of the second compound, there are 72.7 g O and 27.3 g C. The mass of oxygen per gram of carbon is: 72.7 g O / 27.3 g C = 2.66 g O per g C .

Dividing the mass O per g C of the second (larger value) compound: 2.66 / 1.33 = 2. This means that the masses of oxygen that combine with carbon are in a 2:1 ratio.

4. JJ Thomson

a. What subatomic particle is Thomson credited with discovering?

b. What is the name of Thomson’s famous model?

c. Click on the link for Thomson’s experiment and answer the questions below.

Label the parts of the cathode ray tube

d. What does a magnet do to the cathode ray beam?

e. Which direction does the ray bend towards?

f. Thomson’s conclusion was that the cathode ray beam has a _____________ charge.

5. Planck and Quanta

a. Planck’s work with the atomic theory had to do with photons and the ____________ which seemed to be proportional to the frequency of vibration.

b. These quantized “chunks” when multiplied by a constant of ___________________ seemed to take on certain values that Planck called “quanta”.

c. The symbol for Planck’s constant value is _________________.

6: Robert Millikan and the electron charge.

a. What is the name of Millikan’s experiment?

b. What was the purpose of the experiment?

c. How did he accomplish this task?

d. What was the purpose of the Atomizer?

e. What is the charge on a single electron?

7: Ernest Rutherford

a. What is the name of Rutherford’s experiment?

b. What were the expected results of this experiment?

c. What were the actual findings of this experiment?

d. The result of this experiment showed that most of the mass of an atom was located ____________________________ and the overall charge of this region was _________________________.

e.The results of this experiment also showed that most of the size/volume of an atom is composed of __________________________.

f. What actually caused the alpha particles to deflect?

8. Niels Bohr

a. Draw Bohr’s model for helium below.

b. (click on the link on the next slide) Draw and answer the first 3 Bohr model practice problems where you click and drag the parts of the atom based upon the given isotope.

1. given isotope ____________ 2. given isotope _______________ 3. given isotope _________

Draw here

9. Complete the chart below that indicates the parts and locations of those parts of an atom.

Parts of the atom:

|Parts |Charge |Symbol |location |Mass (Kg) |

|Protons | | | | |

|Neutrons | | | | |

|Electrons | | | | |

10. a. What is a quark?

b. How do we use quarks to determine charge in the nucleus?

_____________________________________________End of Power point

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