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There  are  many  kinds  of  light.  Visible light, that you can see with your eyes is just a tiny smidge of a much broader phenomenon (EM radiation). We put all EM radiation on a “spectrum” from the lowest energy to the highest:

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What  is  Light?  (Extended  Remix)  1.  EM Radiation is made of photons. 2.  Photons travel really fast (3.00 x 108 m/s), and

only have mass when they are moving. 3.  Nothing can travel faster than photons. 4.  Photons are particles AND waves. 5.  We focus on three properties of EM waves:

1. The Wavelength (λ) II. The frequency (f) III. The Energy (E)

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Wavelength  (λ)  Wavelength is defined as the distance from one point on a wave to the same point on the next wave. We measure light wavelengths in meter derivatives (just like we measure any length with). Radio Waves:

~103 m Visible Light:

~10-7 m Gamma Rays:

~10-12 m

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Frequency  (f)  Frequency is defined as the number of wavelengths that pass a point in space per second. We measure frequency in Hertz (cycles per second). Radio Waves: ~ 104 Hz Visible Light: ~ 104 Hz Gamma Rays: ~ 1020 Hz

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Here’s  What  You  Need  To  Know:  The more energy a light wave has, the smaller its wavelength is, and the higher its frequency.

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Back  to  Bright  Line  Spectra  As Niels Bohr noticed, when you give a sample of an element some energy, it emits characteristic spectra. It doesn’t produce all of the wavelengths of light.

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Why?  Remember that electrons can only go to specific energy levels when they absorb energy. As a result, they can only emit specific wavelengths of light when they fall back to the ground state. That’s why. We can use this fact to identify the elements that are in distant galaxies, by looking at the light from those galaxies.

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Analysis  of  Spectral  Lines  Resources: •  http://people.westminstercollege.edu/faculty/

ccline/elements/elements1.html

•  http://jersey.uoregon.edu/vlab/elements/Elements.html

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What  now?  

Any  Ques)ons?  

11/30  Objective: SWBAT use flame test data to analyze an element’s electron configuration. Do Now: 1) Hand in work; write the procedure for today’s lab in your lab notebook. 2) Hand in HW. HW – pg. 26 questions.

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Analysis  of  Spectral  Lines  Resources: •  http://people.westminstercollege.edu/faculty/

ccline/elements/elements1.html

•  http://jersey.uoregon.edu/vlab/elements/Elements.html

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12/1  Objective: SWBAT describe how electrons are configured around the nucleus. Do Now: 1) Take out your periodic table and Unit V packet. HW - pg 28- 29in packet

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Unit 5: Electrons Lesson 3: Electron Configuration

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Why  Should  You  Care  About  Electrons?  An atom’s electrons tell us about how the atom will behave physically and chemically. Kernel- All of an atom’s electrons except for the ones in the outermost energy level Valence- the electrons in the outermost energy level.

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1.    Basic  Electron  Configura[on  In a basic configuration, we know how many electrons are in each of the atom’s principal energy levels (PEL’s – aka “shells”). Each PEL has a a specific number of electrons it can fit:

PEL 1 – maximum of 2 electrons PEL 2 – maximum of 8 electrons

PEL 3 – maximum of 18 electrons PEL 4 – maximum of 32 electrons

The basic electron configuration is listed on the periodic table 82  

Look,  it’s  Calcium!  

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How many electrons are in each of calcium’s PEL’s? How many of calcium’s PEL’s are full? How many valence electrons does calcium have?

Bohr  model  of  calcium  

PEL’s  and  The  Periodic  Table  As you can probably see, elements in the same row (aka “period”) of the periodic table all have the same number of electron shells. The number of PEL’s increases by one as you move to higher (lower, really) periods of the table. Q: What do all of the members of a column (aka “group”) of the periodic table have in common? A: They all have the same number of valence electrons!

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2.    Expanded  Electron  Configura[on  Each PEL has sublevel’s. The expanded electron configuration tells you the PEL’s and sublevels of an atom that are filled, and how many electrons are in each sublevel. Sub-levels are designated as s,p,d, and f. We use superscript numbers to denote how many electrons are in a particular sublevel.

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Wri[ng  Expanded  Configura[on  Lithium has the basic configuration of 2-1

Its expanded configuration is 1s2 2s1

Nitrogen has the basic configuration of 2-5 Its expanded configuration is 1s2 2s2 2p3

Magnesium has the basic configuration of 2-8-2 It’s expanded configuration is 1s2 2s2 2p6 3s2

Chlorine has the basic configuration of 2-8-7 It’s expanded configuration is 1s2 2s2 2p6 3s2 3p5

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Filling  can  get  crazy  The basic rule for filling is that electrons will always go in the lowest energy sublevel possible. The only problem with this, is that some sublevels are at a higher energy than other sublevels of higher shells: – The d sublevel of any shell that has one is at a

higher energy than the s sublevel of the next shell. – The f sublevel of any shell that has one is at a

higher energy than the s and p sublevels of the next shell

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Damn,  that’s  confusing  I know, and I’m sorry. The German’s who figured this stuff out came up with a filling order diagram to help us keep it all straight. It’s called the “Aufbau”: Follow the arrows! You can always make your own!!!

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Use  the  Aubau  What is the electron configuration of Potassium?

1s2 2s2 2p6 3s2 3p6 4s1

What is the electron configuration of Iron? 1s2 2s2 2p6 3s2 3p6 4s2 3d6

What is the electron configuration of Bromine? 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

What is the electron configuration of Gold? 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d9

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There  has  to  be  a  lazier  way!  Of course there is. When the electron configuration get’s too funky, we can say that our atom has the configuration of the noble gas (group 18) atom in the previous period by putting that atom’s symbol in square brackets, and then list the remaining expanded notation following that gas. e.g.

Gold: [Xe] 6s2 4f14 5d9

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3.    Orbital  (Box)  Diagrams  In a box diagram we show how many electrons are in each orbital of the sublevel and what the spin of the electron is. Each sublevel has a different number of orbitals:

s has 1 orbital p has 3 orbitals d has 5 orbitals f has 7 orbitals

Each orbital can fit a maximum of two electrons. These electrons have opposing spins, which we call “up and “down”. Box notation shows all of this

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12/2  Objective: SWBAT express the orbital configuration of a given element. Do Now: Draw the box diagram for Li and N. HW – Study for quiz on Bright-line Spectra, electron configuration, and Lewis Dot Diagrams.

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The  Pauli  Exclusion  Principle  An orbital can hold 0, 1, or 2 electrons and if there are two electrons in an orbital, they must have opposite spins.

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Hund’s  Rule  Electrons in orbitals of the same sub-level will always occupy empty orbitals before they will pair up.

Fun  with  Box  Diagrams  Lithium’s Box Diagram: Nitrogen’s Box Diagram:

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Magnesium’s Box Diagram: Chlorine’s Box Diagram:

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Why  should  we  care  about  Boxes?  Box notation is useful for helping us see the unpaired electrons in an atom. Unpaired electrons are involved in chemical bonds. Unpaired electrons are always found only in a ground-state atom’s valence.

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Oh,  I  also  Lied  about  Gold  Earlier, I told you that Gold’s electron configuration was:

[Xe] 6s2 4f14 5d9

It’s actually:

Gold: [Xe] 6s1 4f14 5d10

Can you use box notation to figure out why?

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Shells,  Sublevels,  and  Orbitals  These are three concepts that are related, but can be confusing. Think about it like this: “If electrons were people, they would live in towns called shells (PEL’s), on streets called sublevels and in houses called orbitals. They prefer to live alone, but will live together if they have to. Two electrons can live in each orbital house, as long as they spin in opposite directions.” Different town’s have different numbers of streets and different streets have different numbers of houses.

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4.    Lewis  Dot  Diagrams  Named after Gilbert Newton Lewis. Only show an atom’s valence electrons, surrounding its chemical symbol. Since the valence electrons are involved in bonding, that’s usually the only part of the electron configuration we care about.

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Gilbert  Newton  Lewis  (1875  –  1946)  

Lewis  Diagrams  

Li Be B C

N O F Ne

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More  about  Valence  Electrons  The number of valence electrons is very important for most of the rest of chemistry. Atom’s do what they do because of their valence electrons. Every atom is most stable when it has a full valence shell. The maximum number of valence electrons an atom can have is 8 (except Hydrogen and Helium). Once an atom has 8 valence electrons, it has a “stable octet” configuration. Chemical Bonding is the way that atoms achieve a stable octet. 10

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What  now?  

Any  Ques)ons?  

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