Mr. Davis Baltimore Poly

1. Are electrons more likely to fill the highest or lowest available energy states? 2. What is a valence electron?

 What is the potential energy of an object at height ‘H’ Potential Energy = mgh

 Is the ball’s potential energy increasing or decreasing? Decreasing!!!

 What type of energy transfer is this? Potential Energy to Kinetic Energy

 In your Phet Lab, what happened when the electron was hit by a photon? 1) The electron jumped to a higher energy state 2) Soon after the electron fell back down to the ground state. 3) The electron emits a photon

1) The electron jumped to a higher energy state

2) Soon after the electron fell back down to the ground state.

3) The electron emits a photon

 In your Phet Lab, did the electron spend more time in the ground state or a higher state? The Ground State.

 Electrons work in the same way as the ball does. They tend to have a lower potential energy.

 The lowest band of allowed energy states of an atom.  Band: a range of states.

 Valence electrons reside in the Valence Band.  If given enough energy, electrons can escape the Valence Band.

Conduction Band: Upper band of allowed energy states Electrons are free to move around the crystal /lattice and have very high energies.

 Is the Conduction band more likely to have more or fewer electrons than the Valence band?  MUCH LESS Conduction Electrons must have high energies

 Often Empty ◦ Electrons need energy to get to this band  Electrons only last in this band for fractions of a second ◦ Drop back down to the Valence Band

 Are there more electrons in the Valence band or the Conduction Band?  Valence Band!!!! Electrons in the Conduction Band quickly fall back down to the Valence Band

 The energy needed to break electron bonds in an atom ◦ Releases the electron from its atom  Electron leaves the Valence Band and “jumps” to the conduction band.

 What are different ways we can energize atoms?  Light Increases the energy

 What are different ways we can energize atoms?  Heat Increases the energy

 What is generated when Electrons move through a material?  A Current is caused by moving electrons

 What is a conductor?  A material that permits the flow of electrons

 What is a Insulator?  A material whose electrons do not flow freely

 No band gap ◦ The valence band overlaps the conduction band

 Used in electronics to facilitate electron flow.  What is an example of a Conductor you use everyday?  Power Lines!!!

 Small Band Gap  Used in electronics to transmit electrons

 Thermal energy can bridge the gap for a small fraction of electrons

 At ordinary temperatures, no electrons can “jump” to the conduction band  Prevent the flow of electrons

 Match the description on your desks to one of the three material types we learned yesterday.  Afterwards we will go over it as a class.

 Describe how the band gap of the materials we learned about today, Insulators, Semi-conductors, and Conductors effects the flow of electrons through the material.  Periods 4 and 7

 Match the description on your desks to one of the three material types we learned yesterday.  Afterwards we will go over it as a class.

 What is generated when Electrons move through a material?  A Current is caused by moving electrons

 Describe how electrons move through an Insulator, if they move at all.  In an Insulator current cannot flow freely.

 Describe how electrons move through an Conductor, if they move at all.  In a Conductor electrons can flow freely through the material.

 An Electron in the Conduction Band that moves through the material  Not attached to an atom

 What is Avogadro’s Number?  The number of atoms in a mole of a substance

Number of Free electrons = Free electrons per atom M = Molar Mass m = mass of the substance

 Cadmium has 2 free electrons per atom and a Molar Mass of g/mol. How many free electrons are there in 1g of cadmium?  What is our unknown? ◦ The Number of Free Electrons

 Cadmium has 2 free electrons per atom and a Molar Mass of g/mol. How many free electrons are there in 1g of cadmium?  What are our knowns? ◦ Free Electrons per Atom = 2 ◦ Molar Mass = g/mol. ◦ Mass = 1g

 Cadmium has 2 free electrons per atom and a Molar Mass of g/mol. How many free electrons are there in 1g of cadmium?  What is our equation?

Number of Free electrons = V = Volume

What is the unit for volume? cm 3 or a distance cubed

Number of Free electrons = Number of Free electrons =

ρ =Density

 That was a lot of equations!!!  How will you know when to use which equation?

 Identify your Unknown  Determine your Givens  When solving a problem, WRITE THESE THINGS DOWN

 Silver, with a density of 10.5 g/cm 3 and an atomic mass (molar mass) of g/mol, has one free electron per atom. How many free electrons are there in each cubic centimeter of silver?

 Spend the rest of class working on “Solid-State Electronics”.  It is due Monday.  You must complete three problems by the end of class.

1. At 200.0K, silicon has 1.89 x 10 5 free electrons/cm 3, a density of g/cm 3, and an atomic mass of g/mol. How many free electrons are there per atom at this temperature?

How does doping work in sports? We insert a foreign substance into our bodies to improve performance

 Not in sports but in Semiconductors!  Semiconductor: conducts electricity under some conditions but not others

 Doping- Inserting a different element into a material to change its properties

 Dopant: a trace impurity element that is inserted into a substance  Inserted at LOW Concentrations  Alters the electrical properties

 Goal is to increase the number of free charge carriers (moving electrons).  Add material that takes away our free electrons, causing them to move

 Hole: vacancy left behind by the electron

 Our element wants to have three electrons per table.  Now we want to element p-type doping. Do we want to add a table with more or less electrons?  Less

 Want to create an abundance of holes to increase electron flow.  What is generated when electrons are moving?  A Current!!!!

 Add material that provides us extra free electrons  Creates an excess of negative electron charge carriers

 These Extra Electrons allow for the flow of Current

 Our element wants to have three electrons per table.  Now we want to element n-type doping. Do we want to add a table with more or less electrons?  More

 Device that conducts electricity in only one direction

 Used to: ◦ Tune Radios and TV receivers ◦ Generate Radio Frequencies

 A semiconductor used to amplify and switch electronic signals

  Watch a quick video on transistors  Shows us how this works for all of our technology we use everyday.

 Spend the rest of class working on “Solid-State Electronics”.  It is due Monday.  Exit Ticket at the end of class.

 Based on what you saw in the video and in class today, Describe how the two different types of semiconductors allow for the movement of electrons to generate a current.

1. A metal has 1.92 x free electrons per cubic centimeter. If its atomic mass is g/mol and it has three free electrons per atom, what is its density? Keep your Do Nows Pass in your Homework

 Today we will be headed to the lab, Room 127  The lab is due tomorrow so work diligently.

 At the end of the lab there is a chance to earn bonus points and a bonus assignment.

1) How many atoms of germanium are there in one cubic centimeter of germanium? The density of germanium is 5.35 g/cm 3 and its molar mass is 72.64g/mol. 2) What do the “N” and “P” in the different types of dopants stand for? Pass in your lab

 Today: ◦ Quiz Review, Key at the front and back of the class  Tomorrow: ◦ Tic-Tac-Toe Review ◦ You pick which activities you want to do.

 By the end of class today you need to have completed: ◦ 8 Problems of your Quiz Review ◦ I will come around and stamp this for a grade. ◦ If you finish the Quiz Review you will be given tomorrow’s Review activity.  Group Exit Ticket at the end of class

 What is at least one thing you would like to review as a class tomorrow before the Quiz on Thursday?

1) Cadmium has 2 free electrons per atom. How many free electrons are there in three cubic centimeters of cadmium? ElementDensity (g/cm 3 )Atomic mass (g/mol) Copper Gallium Cadmium Germanium Zinc Indium Aluminum Silicon Sodium

 You can pick any three boxes that give you Tic-Tac-Toe ◦ Two of the boxes require materials from the classroom  The Challenge Problems  Text Book Problems ◦ If you want to work on those boxes, materials are up front.

 By the end of class today you need to have completed: ◦ Two Boxes on your Tic-Tac-Toe Review ◦ I will come around and stamp this for a grade.  Each extra box on the Tic-Tac-Toe Review you complete is an extra point on your quiz ◦ (Up to 6% Extra Credit to your Quiz)

 EXTRA SLIDES AFTER THIS

Variety of ways to build molecules:  Ranges from Simple lattice to Complex shapes