Warm UpWhat is the wavelength defined as?You are given the wavelength of a particle as

being 6.3 x 10 -5 m. What is the frequency of the particle?

You are given the frequency of a particle as 7.43 x 1014 Hz. What is the wavelength?

HINT: Speed of light = 3.00 x 108 m/s

ChemistryUnit Three, Day Two

Kimrey18 September 2012

Electromagnetic SpectrumShows the different types of radiation –

different wavelengths.

Radio Waves

Radio waves are electromagnetic waves with the longest wavelengths (longer than 1mm)

They are used in communications, radar, microwaves, and MRIs

MicrowavesMicrowaves

are radio waves with wavelengths less than 30 cm but longer than 1mm

Cell phones and satellites use microwaves

• Microwaves in microwave ovens cause water molecules to rotate, heating your food

Infrared WavesInfrared waves

have wavelengths between 1mm and 750 billionths of a meter

Thermal energy travels in infrared waves • Remote controls and

CD-ROM drives also use infrared waves

Visible LightThe visible spectrum is the light we can seeIn order from largest wavelength to smallest:

Red, Orange, Yellow, Green, Blue, Indigo, Violet (Roy G Biv)

The color you see is the color that is reflected.

White is all colors, black is no color. The longer the wavelength, the less

penetrating (including less dangerous to cells)

Visible Light

(ROYGBIV)

Ultraviolet Waves Ultraviolet, or UV

waves, have wavelengths of 400 billionths to 10 billionths of a meter

UV waves can cause skin damage such as sunburn, wrinkling, and cancer

Ultraviolet LightUV light enables your

body to make vitamin DUV waves can kill

bacteria by damaging its DNA

X-RaysX-rays have

wavelengths between ten billionths of a meter and ten trillionths of a meter

X rays are commonly used by doctors

and dentists

Gamma Rays

Gamma waves have wavelengths shorter than 10 trillionths of a meter

Gamma rays are produced by radioactive decay or other subatomic processes

The Bohr Model Created by Niels Bohr in 1913.Related the energy of an electron to the

orbital it would occupy. Similar to the model of the solar system with

the nucleus as the sun.

• 1st shell can hold 2 electrons.• 2nd can hold 8.• 3rd can hold 18• 4th can hold 32

Making Bohr ModelsStep One: Write the number of protons and

neutrons in the nucleus. Step Two: Add electrons in their appropriate

orbitals until you have reached the correct number of electrons.

ExampleDraw a Bohr model for Mg-24.

You TryDraw a Bohr model for the following:

Nitrogen-14Aluminum -27Sodium-23+1

Conclusions from the Bohr ModelElectrons are both Particles AND waves. We cannot know for certain where an

electron is.We cannot know for certain how fast an

electron is moving. The more we know about the location of an

electron the less we know about its’ movement and vice versa.

Bohr Model and LightBohr went a step further as well, he

determined that each orbital corresponded to a certain energy level.

As electrons become excited they can “jump” to a higher energy level.

When these electrons return to their ground state (normal energy level) they emit the difference in energy levels.

NOTE!!! Electrons can ONLY exist at a specific orbital NOT between orbitals.

Reading the Bohr Model

ExampleWhat is the wavelength of light emitted when

an electron goes energy level 4 to energy level 1?

(n=4 n=1)97 nm

You TryWhat is the wavelength of light emitted when

an electron goes from n= 3 to n = 2?What type of light would this be classified as? A photon with a wavelength of 656 nm is

emitted from a hydrogen atom. What energy state did this electron start in and end in?

Bohr Model for H Atom

Example ProblemsWhat type of light has a wavelength of 1 x 10-11 m? What type of light is released when an electron jumps

from = 4 to n = 1 in a Hydrogen atom?What type of light has a wavelength of 6.3 x 10 -7m?Is light energy released or absorbed in the following

jumps of an electron in a Hydrogen atom?n=1 to n = 3 n = 2 to n = 5 n = 6 to n = 3n = 2 to n = 3

Rank the following types of light in increasing energy:X – ray, green light, microwaves, violet light.