FACT: Chemical reactions happen because electrons are shared or transferred from one substance to another

MAX NUMBER OF ELECTRONS IN AN ENERGY LEVEL ENERGY LEVELMAX # OF ELECTRONS

Write a mathematical equation that allows us to predict the Max # if we know the energy level (n) ENERGY LEVELMAX # OF ELECTRONS Max # = …n…

Equation to calculate Max # of e - 2n 2 Where n is any energy level

On the Back of your Max # of Elections Sheet Bohr Models Draw the Bohr Structures for elements 1-18

WHITEBOARDING Bohr Models Draw the Bohr Structure for Z=19 (Potassium)

Catalyst Draw the Bohr Structure for Z=19 (Potassium)

Obviously something is wrong…because the electrons fill in an unexpected order. We need a more complicated system!

There are 4 Quantum #s and those #s are used to describe where an electron is likely to be found at any given time

This is a lot like being able to use four “places” to describe EXACTLY where Mr. C should be at 8:00AM on Friday.

The first number we already know… The Principle Quantum # (b.k.a. The NRG level)

1 st Quantum # Principle Quantum # Specifies the energy level that the electron is on

Principle Quantum # (IDEA Academy’s Street)

But this doesn’t explain why K’s last electron goes into the 4 th energy level instead of the 3 rd

2 nd Quantum # Specifies the shape of the sub-energy level

Second Quantum # (IDEA Academy)

s and p Sub Energy Levels

III. Quantum Mechanical Model: Atomic Orbitals E. Shapes of orbitals d orbitals

ORBITAL Space occupied by a pair of electrons

Four Sub-Energy Levels Sub NRG Level ShapeMax # of electrons # of Orbitals sSphere21 pDumbbell63 d4-Lobed105 f6-8 Lobed147

Sub-Energy Levels

So why do electrons fill in like they do? i.e. why is K’s last electron in the 4 th NRG level?

2 Factors Influencing Electron Placement 1.Energy Level - Closer to nucleus=easy 2. Subenergy level (shape) - s  p  d  f

Electron Configuration A detailed way of showing the order in which electrons fill in around the nucleus

Electron Configuration Symbols 5f 35f 3 Energy Level Sub-Energy Level # of e - in sub-energy level

Electron Configuration PT

K K: 2s 2 1s 2 4s 1 3s 2 2p 6 3p 6 Bohr Models vs. e - Configs

Write the e - config for: H: 1s 1 He: 1s 2 Li: 1s 2 2s 1 K: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1

HOMEWORK Do Worksheet entitled “Electron Configurations” Due

Again… Why are we concerned so much about electrons?

So do we really need to know about all of the electrons?

e - configs with the NGSC represent which electons?

Valence Electrons Electrons in the outermost energy level (involved in chemical reactions)

Noble Gas Shortcut K: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 K: [Ar] 4s 1 So what is different?

Aufbau Principle All lower energy sublevels must be full before high energy sublevels begin filling in

Steps for writing NGSC 1.Write the noble gas preceding the desired element [in brackets] 2. Carry on as usual

With only the first two Quantum #s, do we have as much information as possible as to where the electrons are likely to be found?

3 rd Quantum # m or magnetic Q# Specifies the orientation of an orbital in space

Third Quantum # (Mr. C’s Office)

4 th Quantum # s or spin Q# Spin of an electron on its own axis

Fourth Quantum # (Mr. T’s Desk)

Quantum Review 1 st Q#: Energy Level 2 nd Q#: Shape of sub 3 rd Q#: Orientation of Orbital 4 th Q#: Spin of e -

Principle (n): 1, 2, 3, 4, … Azimuthal (l): 0, 1, 2, 3 Magnetic (m l ): …-2, -1, 0, 1, 2 Spin (m s ): +1/2 or -1/2

Pauli Exclusion Principle No 2 electrons can have the same set of 4 quantum numbers

Arrow-Orbital Diagrams A way to show orbital filling, spin, relative energy

Hund’s Rule Most stable arrangement of electrons is the one with the maximum number of unpaired electrons

Arrow-Orbital Diagrams Energy 1s 2s 2p 3p 3s 4s 3d

Lewis Electron Dot Diagrams The easiest way to represent the # of valance electrons

Steps for writing electron dot diagrams 1.Write the element’s symbol 2.Write out e - config 3. Count # of valence e -s (1-8) 4. Place same # of dots as e - around symbol

Order to fill in an e - dot Bm

What up? Bm 1 2 Why do 1 and 2 fill in on the same side? Who do 1 and 2 represent?

What up? Bm Who do 3-8 represent? Why do 3,4,5 and 6,7,8 fill in on different sides?

What up? Bm Why will you never have more than eight dots? 1 2

Examples of Lewis Electron Dots

What is different between the dot diagrams below and the ones that we’ve been doing? Our way accounts for Quantum #s, this way doesn’t!

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Flame Tests Certain elements emit specific wavelengths of light when the electrons fall from outer energy levels back to their ground state.

The Electromagnetic Spectrum

Line Spectra of Excited Atoms Excited atoms emit light of only certain wavelengths The wavelengths of emitted light depend on the element. H Hg Ne