Unit 2: Atoms and Bonding

2.61 LightTextbook ch 6.1

Big Idea 1: The chemical elements are fundamental building materials of matter, and all matter can be understood in terms of arrangements of atoms. These atoms retain their identity in chemical reactions. Students will be able to demonstrate understanding by laboratory investigation, analysis of data and creation of models.

SWBAT:•Calculate the wavelength of electromagnetic radiation given its frequency or its frequency given its wavelength

•Order the common kinds of radiation in the electromagnetic spectrum according to their wavelength or energy

Learning Objectives:

The ELECTRON: Wave – Particle Duality

Graphic: www.lab-initio.com

The Dilemma of the Atom

• Electrons outside the nucleus are attracted to the protons in the nucleus

• Charged particles moving in curved paths lose energy

• What keeps the atom from collapsing?

Wave-Particle DualityJJ Thomson won the Nobel prize for describing the electron as a particle.His son, George Thomson won the Nobel prize for describing the wave-like nature of the electron. The

electron is a

particle!

The electron is an energy

wave!

The Wave-like Electron

Louis deBroglie

The electron propagates through space as an energy

wave. To understand the atom, one must understand

the behavior of electromagnetic waves.

Waves• Wavelength= measured crest to crest• Frequency = # of complete wavelengths or

cycles• That pass a certain point per second

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=DaMB0aK1DXiivM&tbnid=oMaSLnYCovrnEM:&ved=0CAUQjRw&url=http://www.chem.ufl.edu/~itl/2045/lectures/lec_10.html&ei=HUY2UvKzGdbI4APi6YBw&psig=AFQjCNFAz0LZbG5carvKH4p7C2gQ9lphlQ&ust=1379374854454275

Parts of A Wave

wavelengthdistance between two consecutive peaks or troughs in a wavesymbol: lambda, lunits: meters (m)  

frequencythe number of waves passing a point in a given amount of time symbol: nu, nunits: cycles/sec or 1/sec or sec-1 or Hertz (Hz)

peak/crest

trough

node

c = nlc = speed of light, a constant (3.00 x 108 m/s)n = frequency, in units of hertz (hz or sec-1)l = wavelength, in meters

Electromagnetic radiation propagates through space as a wave moving at the speed of light.

Conversions needed to do these problems

1nm = 1 x 10 -9 m

1hz = 1/s = 1 s -1

Hz = hertz, a unit for frequencys = secondss -1 = per second

The Electromagnetic Spectrum

Gamma rays wavelength similar to diameter of atomic nuclei

Gamma rays

Radio waves longer than a football field

Increasing

1. Which wave has a higher frequency?

2. Which wave has a longer wavelength?

3. If one represents blue light and one represents red light- which is which?

Try this one…

• The yellow light given off by a sodium vapor light has a wavelength of 589nm. What is the frequency of this radiation?

References

Our textbook: Brown, Lemay et all. AP edition chemistry, 13th edition, 2015

www.sciencegeek.net/Chemistryand Mr. Perekupa’s PPT Cinnaminson.com from Cinnaminson High school.

I modified the original PPTs to fit our needs in AP Chemistry.