Bellwork (…to be done when you walk in)

• Write down three facts that you know about electrons.

Unit 3: Electrons in Atoms

Mr. GatesCh. 5

Prentice Hall Chemistry

Learning objective

• I can define “electron configuration.”

• I can write the electron for a given element.

Orbitals

• Schrodinger developed the Quantum Mechanical Model which described the location of electrons based on probability.• Atomic orbitals are regions in space with the

highest probability of finding an electron.

Main Types of Orbitals

Dumbbell

Electron Configuration

•Electron Configuration: the way electrons are arranged around the nucleus of an atom.

Aufbau Diagrams

Electron Configurations Rule #1

• Aufbau Principle: electrons enter orbitals with the lowest energy first

Electron Configurations Rule #2

•Pauli Exclusion Principle: a suborbital can hold a maximum of TWO electrons each of opposite spins.

Electron Configurations Rule #3

•Hund’s Rule: When electrons occupy suborbitals of equal energy, one electrons enters each suborbital until each has an electron of parallel spins, before entering a second electron into the suborbital. • Half fill each suborbital before completely filling

any suborbital of the same energy.

Example of Hund’s Rule

Practice

• Fill in the energy level diagram (aufbau diagram) on the right for a neutral oxygen atom.

Practice… solution

• Fill in the energy level diagram (aufbau diagram) on the right for a neutral oxygen atom.

Writing Electron Configurations

Examples

•K• 1s22s22p63s23p64s1

•O• 1s22s22p4

•Cl• 1s22s22p63s23p5

Exit task

• Write down the electron configuration of Nitrogen.

Noble Gas Notation

• K• 1s22s22p63s23p64s1 • [Ar] 4s1

•O• 1s22s22p4 • [He] 2s22p4

• Cl• 1s22s22p63s23p5

• [Ne] 3s23p5

Learning Objective

• I can identify the trend of electron configurations on the periodic table.

Tricks of the Trade

•s = same as period number•p = same as period number•d = period number minus 1• f = period number minus 2

Periodic Table and Orbitals

Orbital Notation

•Represents how orbitals fill using lines and arrows

Orbital Notation

*Exceptional Electron Configurations

• All elements up to V follow the normal e- configurations• After that there are exceptions• Sometimes electrons rearrange

themselves so orbitals are full or half-full instead of partially full

*Exceptional Electron Configurations

Expected e- configuration• Cr 1s22s22p63s23p64s23d4

• Cu 1s22s22p63s23p64s23d9

Predicted e- configuration• Cr

1s22s22p63s23p64s13d5

• Cu 1s22s22p63s23p64s13d10

Bellwork… start working on as soon as you get to class.

•Work with a partner to brainstorm as many sources of light as you can think of that you have encountered in your life. • Examples: sun, light bulbs, fireworks, etc.

•Answer the question: is all light visible?

Light… particle or wave?

• Early scientists believed that light behaved as a wave.

• Later evidence suggested that light behaves like a particle.

• https://www.youtube.com/watch?feature=player_detailpage&list=PLJicmE8fK0EiEzttYMD1zYkT-SmNf323z&v=Hk3fgjHNQ2Q

Parts of a Wave

• Wavelength ( λ - lambda )- the distance between crests• Amplitude- the height of a wave from the origin

to the crest

Frequency (v)

• Frequency is the number of wave cycles to pass a given point per unit of time. • Units are usually cycles per second• The SI unit of cycles per

second is called a hertz (Hz)• Hertz can also be expressed

as inverse seconds (s-)

Assessment for learning

• Draw a line about 5in long in your notes and draw two waves on this line with the same amplitude, but different frequencies.

• Draw a line about 5in long and draw two waves on the line with the same wavelengths, but with different amplitudes.

Relationship between (v) and (λ)

• Frequency and Wavelength are inversely proportional. • As one goes up, the other

goes down.

• The speed of all light is constant.• c (speed of light) = 3.0 x 108

m/s• c = vλ

Practice

• What is the frequency of light that has the wavelength of 1.2 x 10-5m?• 2.5 x 1013 s-

• What is the wavelength of light that has a frequency of 4.35 x 1018s- ?• 6.9 x 10-11m

Mo’ Practice, Mo’ Perfect

•A red light has a wavelength of 728 nm.  What is the frequency of the light? (1 nm = 10-9 m)

•A purple light has a frequency of 7.42 x 1014 Hz.  What is its wavelength?

Electromagnetic Spectrum

Homework

• Pg. 146• # 16, 21

• Pg. 149• # 40, 42, 45, 46,

Energy and Light

• Energy of a light wave is directly related to the frequency. • Higher energy = higher frequency

•E = h x v •Where:• E = Energy (J)• h = 6.626 x 10-34 Js• v = Frequency (Hz)

Let’s get excited!!!

• When people get excited, their level of energy as displayed to those around them increases.

• When electrons get excited, their level of energy increases as well

• When electrons become de-excited, their level of energy drops.

Started from the bottom…

• An electron in its lowest possible energy state is in its ground state.

Excited Electrons

• As electrons become excited, they jump up to an orbital of a higher energy level.• This is caused by an absorbance of

energy.• As electrons become de-excited,

they drop to an orbital of a lower energy level. • This causes a release or emission

of energy.

To Excite or Not Excite

• An electron must absorb/emit exactly the energy equal to the difference between the energy level it is at and the energy level it will be excited/de-excited into, in order for the electron to move between orbitals. • More or less than exactly the energy gap will

result in NO CHANGE.

Energy Emissions

• Energy is emitted in the form of light. • The type of light that is emitted depends on how far an electron falls.• The farther an electron falls, the greater the energy and the frequency of the light it emits.

Light and the Atom

• If there are multiple electrons, then multiple frequencies of light can be emitted.

•Different elements release different colors of light.

Atomic Emission Spectrum

• The different frequencies of light that are released can be observed and recorded to produce an Atomic Emission Spectrum.• This can be used as a “signature” for an element

Practice Calculations

•What is the energy of a photon whose frequency is 3.0 X 1012 Hz?

• Calculate the photon energy of light (in J) with a wavelength of 254 nm

Homework

•Pg. 146•# 17, 18,

•Pg. 149•# 47,

•Pg. 151•# 76