Light and Planck's Constant

Notes for Page 29.

Review: (all Review Points taken from Page 17)
1) Energy of electrons increases as you move away from the nucleus.
2) You cannot pinpoint the exact location of an electron - only the general area (Heisenburg Uncertainty Principle - loosely)
3) Bohr put electrons in orbitals.

Waves:

Frequency is inversly proportional to wavelength

- As frequency increases, wavelength decreases (gets shorter)
- As frequency decreases, wavelength increases (gets longer)

The formula for the relationship between frequency and wavelength is:

Why do I care about waves?

 1) Light travels in waves

 2) Electrons are made of light

Light

- Travels in waves

- Very fast

- Electromagnetic Spectrum



How does this apply to Chemistry?

- Electrons are photons of light

- Atoms have an emission spectrum!

   * called the Atomic Emission Spectrum

   * Unique to each element

      (this is how they determine what stars are made of)

   * Seen when an excited atom passes through a gas

How does it work?

1) Atom absorbs a certain amount of energy

2) Atom moves to a higher energy level (now called "excited")

3) Moves back down to its normal energy level (Ground State)

    - emits a packet of energy (quanta or photon) as it does this

4) We can see this emission of energy

    - comes out as color!

Photoelectric Effect

- Metals heat up and change color

- Max Planck wanted to explain this change of color

  * determined that energy changes in set units (quanta)

- Planck's Constant

  * Pertains to amount of energy released when an excited electron goes back to its Ground State

  * States: The amount of radiant energy (E) absorbed or emitted is proportional to the frequency of the

     radiation absorbed.

Planck's Constant = 6.6262 x 10 ^-34 Js

Websites:
Click Here for an explanation of quanta, or photon.
Click Here for an explanation of Planck's Constant.
Click Here for the history and explanation of Planck's Constant.

Bohr Diagram

Things you need to know before you can draw Bohr Structures:

Atoms contain protons, neutrons, and electrons.

Protons

• Positively charged
• Located in the Nucleus
• Contribute to Mass
• Contribute to Charge
• Tell you which element you have
• # CANNOT change
• Are = to the Atomic Number

Neutrons

• Neutrally charged
• Located in the Nucleus
• Contribute to mass
• # CAN change (isotopes)

Electrons

• Negatively charged
• Located in the orbitals
• No mass
• Contribute to charge
• # CAN change

***Assume, for now, that all atoms are neutral. This means that #protons = #electrons***

Bohr Structure

• Shows ALL electrons
• Maps electrons in their orbitals

Orbitals can hold electrons. (n = orbital #)

• Orbital #1 can hold 2 electrons.
• Orbital #2 can hold 8 electrons.
• Orbital #3 can hold 18 electrons.
• Orbital #4 can hold 32 electrons.

Steps:

1. Ask yourself "How many protons are there in this neutral atom?"
2. Based on Mass #, determine number of nuetrons.
3. Since it's a neutral atom: # p = # e
4. Draw orbitals (# orbitals = Period #)
5. Place electrons in orbitals

How to place electrons:

1. Orbital #1 - electrons pair together at the top of the circle
2. All other Orbitals - electrons are place one at a time starting at the top, moving clockwise
3. Once you have four electrons in an orbital the electrons start pairing up.
4. Once you reach the max number that an orbital can hold you move to the next orbital.

Average Atomic Mass

Every element has at least 2 naturally occurring isotopes.

This begs the question, "If elements can have different masses, why is there only one mass on the Periodic Table?"

The mass on the Periodic Table is actually the Average Atomic Mass of all of that element's isotopes.

Quick notes on Average Atomic Mass:

• Units: amu (Atomic Mass Unit)
• The mass on the PT
• Comprised of the average of all isotopic masses

This is the formula for Average Atomic Mass:



This is what the formula means:

1. Isotopes don't exist in equal amounts
2. Take each isotope's mass
3. Multiply it by its % abundance (in decimal form)
4. Do this for all isotopes of the element
5. Add them together

Ex.

Carbon has 2 main isotopes: Carbon-12 and Carbon-13.

C-12 makes up about 98% of all of the Carbon in the world.
C-13 makes up about 1.1% of all of the Carbon in the world.

To find the Average Atomic Mass of Carbon:

1) Change % to decimal

98% = .98
1.1% = .011

2) Multiply decimal by corresponding mass

.98 x 12 = 11.76 amu
.011 x 13 = .143 amu

3) Add the products together

11.76 amu + .143 amu = 11.903 amu

4) The Average Atomic Mass of Carbon is 11.903 amu

Websites
Here is a video explaining how to calculate Average Atomic Mass.
This website gives a brief explanation and a few examples.
Worksheets
This is a great worksheet on Average Atomic Mass.

Extra Credit Opportunity #2

Extra Credit Opportunity
Due: Monday, September 19

Create Flashcards of the following:

1. Scientists involved in Atomic Theory Development (7)
    Front: Name of Scientist
    Back: Year, contribution, experiment

2. Scientists involved in the Development of the Modern Periodic
    Table (6)
    Front: Name of Scientist
    Back: How he arranged the PT, what he contributed

3. Ions (2)
    Front: Type of Ion
    Back: Definition, what causes ions to form

4. Isotopes (1)
    Front: Isotope
    Back: Definition, what causes isotopes to form

5. Subatomic Particles (3)
    Front: Name of subatomic particle
    Back: Charge, mass, location

6. Families (4)
    Front: Family Name
    Back: Group #

Isotopes and Ions

Notes for Page 23.

Atoms are identified by their # of protons.

• The # of protons DOES NOT change
• The # of neutrons CAN change
• The # of electrons CAN change

When the # of neutrons and electrons change the atomic structure/description also changes.

Isotopes

• Atoms of the SAME element with DIFFERENT atomic masses
• Occur when a change in neutrons occurs
• All elements have at least two naturally occurring elements

Two ways to write isotopes

1)

Ex.

2)

Ex.

Ions

• Atoms with a charge
• Occur when there is a change in # of electrons

Two types:

1) Cation - positively charged ion

2) Anion - negatively charged ion

Charge is written in the top right corner of the chemical symbol

Quizzes

Quiz #1 is a great quiz!

Quiz #2 is another great quiz!

Quiz #3 is a very basic matching quiz.

Quiz #4 is a really great quiz.

Worksheets

This is a great worksheet on the Subatomic Chart that includes Isotopes and Ions.

This is a great worksheet on atomic structure with isotopes and ions.

PT Review and Intro to Atomic Structure

Notes for Page 21.

In neutral (n) atoms
       Proton # is = to Electron #.

In all atoms
     Mass # is = p + n

Atoms
- Smallest unit of an element that retains elemental properites
   (Dalton's Postulates)
- Are made of Subatomic particles (sub = smaller than, atomic = atom: smaller than an atom)
    1) Protons
         * found in the nucleus
         * charge of +1
         * mass = 1 amu
    2) Neutrons
         * found in the nucleus
         * no charge (neutral)
         * mass = 1 amu
    3) Electrons
         * found in the electron cloud
         * charge of -1
         * negligible (no) mass

History of the Periodic Table

Notes for Page 19.

Click here to download the PowerPoint presentation from class.

If you are unable to download the PowerPoint, please email me at EORoark713@gmail.com or at Elizabeth.Roark@aliefisd.net.

*Please allow 24 hours for a response.

History of the Atomic Theory

Notes for Page 17.

Click here to download the PowerPoint presentation from class.

If you are unable to download, please email me at EORoark713@gmail.com or at Elizabeth.Roark@aliefisd.net.

*Please allow 24 hours for a response.

Accuracy vs. Precision

Notes for Page 15.

Science is based on measurement.
Scientists test the same measurement over and over.

Accuracy
Closeness to the True Value
When a measurement equals the True Value

True Value is what you expect to get.
It is also referred to as the Accepted Value or the Given Value.

Ex.
Hits the Bulls eye

Precision
Degree of reproduce-ability
When you get the same number over and over.

You can be precise, but not accurate.
You can be accurate, but not precise.
You can be precise and accurate.

Websites

This website has explanations as well as examples.

The Periodic Table of Elements

Notes for Page 13

Chemistry hinges on The Periodic Table.

This is the Periodic Table that will be given to you when you take TAKS. (click to view a larger picture)

You can find multiple things on this Periodic Table (PT from here on out).

1) At the top is a picture of the element Silicon. In this picture, TAKS shows you where the Atomic Number, Atomic Mass, Symbol, and Name can be found.

Atomic Number = # of protons
Atomic Mass = average atomic mass of the element, # protons + # neutrons

2) Across the top of the PT are Roman Numerals IA-VIIIA. These are called Groups and will help you find valence electron number and oxidation number.

3) Down the PT are numbers 1-7. These are referred to as Periods and tell you how many orbitals an element has.

4) There is a bold line that looks like a "staircase." Along this line are the elements Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, and Polonium. These are Metalloids.

5) To the left of the metalloids are metals. To the right of the metalloids are non-metals.

6) The elements in Group 1 are the Alkali Metals.

7) The elements in Group 2 are the Alkaline Earth Metals.

8) The elements in Groups 3-12 are the Transition Metals.

9) The elements in Group 17 are the Halogens.

10) The elements in Group 18 are the Noble Gases.

Websites

This is a great website that shows the PT according to names of groups and allows you to click on individual elements.

Significant Figures

Scientists use varying pieces of equipment. Different pieces of equipment measure to a different degree of preciseness.
For example : One scale might measure to the hundredths place (.12) while another scale might measure to the thousandths (.120).

We have to account for this when we add, subtract, multiply, or divide numbers of varying preciseness.

We do this by using Significant Figures.

Rules:

1. Any non-zero number (1-9) is significant.
Ex.
      12 has 2 significant figures: 12
           - both 1 and 2 are non-zeroes

      12.3 has 3 significant figures:  12.3
           - 1, 2, and 3 are non-zeroes

2. Any zero between a non-zero is significant.
Ex.
      101 has 3 significant figures: 101
           - 1 is significant (Rule #1)
           - the zero is between the ones     
    
     1002 has 4 significant figures: 1001
          - 1 and 2 are significant (Rule #1)
                - the 2 zeroes between them are significant

3. Any zero before the first non-zero is not significant.
Ex.
      0.102 has 3 significant figures: 0.102 
          - 1 and 2 are significant (Rule #1)
               - the zero between the 1 and 2 is significant (Rule #2)
               - The first zero is not significant because it comes before the first non-zero.    
     
      0.00012 has 2 significant figures: 0.00012
           - 1 and 2 are significant (Rule #1)
               - All of the zeroes are before the first non-zero and are not significant

4. Any zero after a non-zero with a decimal point is significant.
Ex.
      1.0 has 2 sig figs: 1.0 
          - the 1 is significant (Rule #1)
               - the 0 is significant because there is a decimal     

     1.2030 has 5 sig figs: 1.2030 
          - the 1,2, and 3 are significant (Rule #1)
              - the first zero is between two non-zeros and is significant (Rule #2)
              - the last zero is after the last non-zero and there is a decimal point.

5. Any zero after a non-zero without a decimal point is not significant.
Ex.
      10 only has 1 sig fig: 10
         - 1 is significant (Rule #1)
              - there is no decimal point     
  
     1010 has 3 sig figs: 1010 
         - 1 is significant (Rule #1)
             - the first zero is between two non-zeros (Rule #2)
             - the last zero is not accompanied by a decimal and is therefore not significant.

Adding and Subtracting
When you add or subtract numbers the answer should be rounded to the lowest number of decimal places.

Steps:
1) Add or subtract as the problem states.
        12.03 + 1.9 = 13.93

2) Identify # of decimal places
        12.03 + 1.9 = 13.93Ex.
             2 dp          1dp 

3) Identify lowest number of decimal places
        1.9 has only 1 decimal place

4) Round answer to match the lowest number of decimal places
       Since the lowest number of decimal places is 1 my answer can
       only have 1 decimal place.
      13.93 is rounded to 13.9.

5) Correct Answer: 13.9

      2.5233 - .125874 = 2.397426
          4 dp                6dp               2.3974 is the correct answer    
   
      35.63 + .2586 = 35.8886
        2 dp             4 dp         35.89 is the correct answer

Multiplication and Division
When you multiply or divide numbers the answer should be rounded to the lowest number of significant figures.

Steps:
1) Carry out multiplication or division as usual.
      12 x 30 = 360

2) Identify numbers of significant figures.
     12 has 2 sig figs (Rule #1)
     30 has 1 sig fig (Rule #1 and #5)

3) Identify lowest number of sig figs
     30 has 1 sig fig which is the lowest number of sig figs

4) Round the answer to the lowest number of sig figs.
    360 has 2 sig figs (Rule #1 and #5) and will round to 400 to match 1 sig
    fig.

5) Correct Answer: 400

Ex.
      30560 x 101 = 3086560
       4 sig figs      3 sig figs    3090000 is the correct answer
         (R #1,2,5)   (R #1,2)     
 
      65 / 200 = 0.325
      2 sf      1 sf         0.3 is the correct answer
      (R#1)    (R#1,5)   *Note that the 2 and 5 are not turned to 0s like in the first example. These zeroes
                                                  would be significant based on Rule #4 and would give the answer 3 sig figs.

Websites:
                      
Replacement Assignment print this out and turn it in on Tuesday, September 6. If you are using it to replace Significant Figures Homework on Page 10 it must be turned in on Tuesday. If you are using it as extra credit you have until Friday.

Click here for an awesome explanation of rules with great examples.   

Intensive/Extensive

There are two categories of physical properties:
1) Intensive
2) Extensive

Intensive
Intensive properties are properties that are independent of the amount of matter present.

Ex.

Color - your hair remains the same color after you cut it (decrease the amount of matter present)

DENSITY - density is a ratio and does not change if the state of matter remains the same

Odor - 1/2 of a lemon smells like a lemon, 1/4 of a lemon smells like a lemon

Boiling point - 100 mL of water will boil at 100 degrees F, 200 mL of water will boil at 100 degrees F

Freezing point - 100 mL of water will freeze at 0 degrees F, 200 mL of water will freeze at 0 degrees F

Extensive
Properties that depend on the amount of matter present.

Ex.

Measurements - if I cut a 6 inches straw in half (remove matter), it is no longer 6 inches

Mass - if I remove 5 g from a 10 g sample (remove matter), it no longer weighs 10 g

Volume - if I add 10 mL to a 5 mL (add matter), it no longer has a volume of 5 mL