Chapter 4, waves, light and electrons Electromagnetic spectrum!!!

Electromagnetic spectrum  Electromagnetic spectrum is any type of energy that moves at the speed of light.  C ( speed of light) = 3.0 x cm / second  m / second C=( 3 x 10 8 m/ second )  Visible light, radio waves, Ultraviolet light, x rays,  infrared light, t.v. waves, microwaves, gamma waves

What hurts, what doesn’t  Gamma are most damaging  X rays  Ultraviolet  Visible light  Infrared  Microwaves  T.V and radio waves

Continuous spectrum  Each type of light has several parts  ( visible light is red, purple, yellow etc)  So a set is called continuous,  Each part of a set is a line spectrum  (red is a line, purple is a line)

Speed of light  Speed of light is dependant on 2 things, the wavelength and the frequency of the wave.  C = w X F or c =  C=speed, = wavelength = frequency  C= 3.0 x cm/sec, and wavelength of red light is 6.0 x cm, what is the frequency?

SI unit for frequency is hertz. Hz. One wave per second. If this picture were a second, there would be 4 hertz. Wavelength is the distance from crest to crest or trough to trough. Amplitude is the height of the wave, but it isn’t as important for light as for sound, so that is all you need

How are wavelength and frequency related? Which line has greater wavelength? Which has greater frequency? Wavelength and frequency are inversely related

Frequency and Energy The higher the frequency, the more energy of the wave This is a direct relationship ( this is why gamma rays and x rays are dangerous, but microwaves are not!!!! E = h v ( h= x ) E- energy h-plank’s constant, v is still frequency

Lets try some!  If purple light as a wavelength of 4 x10 -7 m, what is its frequency?  What is its energy?

Quiz over speed of light  1 what is the speed of light?  2. list 3 parts of the electromagnetic spectrum  3. Name one type of electromagnetic energy that is not safe for you  4. if the frequency of x rays is 2.1 x hertz what is the wavelength?

Plank was working on relating energy of a wave to it’s frequency. Said they are directly related!!!

Plank also worked on 2 major problems of his time. Both were problems with light and energy, but were solved with chemistry. Photoelectric effect Light escaping by hot matter

hot matter should give off UV light, but does give off visible light and photoelectric effect- states that only high frequency light ( even short time) causes e- to move, but low energy light should.

How he solved the photoelectric effect  Sometimes waves act like particles Photons for visible light Quantum for all other EMR. Quantum is a set “particle” of energy (quanta is plural)

This applies to electrons as well. They usually act like a particle, but can have properties of waves!!! Electrons move around the nucleus in a set pattern, but energy can get them to move away from the nucleus, and as they come back, give off light!!!! m

Ground state- Place where electrons hang out normally Excited state- where electrons go when energy is added! As electrons “fall back” to ground state, give off light! Fireworks, flares, stars, sparks!!!

 s/orbitsorbitals.html

Line emission spectrum  A line emission spectrum is the set of colors each element gives off as it’s particular electrons move  Bohr that first figured this out. Worked with Hydrogen, which is lavender!!! 

Bohr was only partly right!!  Bohr thought that electrons traveled around the nucleus like planets around the sun- in an orbit. ( 2D path )  Schrodinger- rethought orbits into 3D orbitals, gave the electrons whole areas to move in, this fit the Line Emission Spectrum better.

Other people of this time  DeBrogli- used the idea of quantum to explain other wavelike behavior of atoms, used the math to get frequencies and energy.  Einstein- Worked with Plank and others, gave the idea of applying quanta to all EMR (gamma, x rays tv rays etc)

How electrons move  4 ways to describe movement of electrons, like an address. Call them all quantum numbers, though they aren’t all #’s. Principle quantum number- distance from nucleus, a number is always first, and closest to the nucleus, number gets higher as they move away Angular momentum- a shape that describes their orbital, s, sphere p, a dumbell or infinity sigh d, a four leaf clover f unknown omic%20Orbital%20Pictures.html#4p_orbital omic%20Orbital%20Pictures.html#4p_orbital

The 3rd of the address  3 rd part of address Magnetic quantum number- it has to do with direction in space, x axis, y axix, z axis, or combinations of those 1 s magnetic # 1s 3 p magnetic # ( p x p y p z) 5 d magnetic # ( dx, dy, dz, dxy, dxz) 7 f magnetic # ( don’t know, who cares, just know there are 7!!!)

The last part!!! It is easy!  The 4 th part of the address is the direction the electron is spinning!  Called the spin quantum number  Clockwise or counter clockwise!!!

Tips to writing electron addesses  Electron configuration is the name  A “1” orbital only has 1 shape, (s) “2” has 2 shapes- s and p, “3” has 3 – spd and 4 and up all have spdf. Each magnetic # has a clockwise and counter clockwise electron in it.

How some look  Hydrogen 1s  Lithium 1s 2s

Other people who contributed . Pauli- created exclusion principle which states that no two electrons can have the same 4 quantum numbers  Heisenburg- Uncertainty principle which says you can’t tell speed and location of a moving object at the same time.  the Aufbau principle –not a person, a term that explains that lowest energy level fills first

More people and ideas  Hund- it is he who said that electrons will fill equal energy orbitals SEPERATLY until they are forced to PAIR UP  So you write ↑ ↑ ↑ not ↑↓ ↑  p

How to fill in d and f  When you get to element 21 you get to fill in D’s. Just remember ( and write on your periodic table) that they are one number lower.  So 4s2 3d10 4p6, then on and on  For the F’s- ok, follow along on your periodic table

Lets try to write for Tungsten  Tungsten has 74 electrons.  1 st put on your periodic table at # 58 that those are 4f’s and # 90 is 5f’s  How many electrons are we writing?  Yep, 74  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 5d 1 4f 14 5d 3

Try these  SulferHydrogen  CesiumPlatinum  UraniumChlorine  PotassiumKrypton  HafniumAluminum

Noble gas notation  Use the noble gas from the row before ( it is row 18) then only have to fill in new stuff!  N- it is like Helium but 2s 2, 2p 3 so  N {He} 2s 2, 2p 3  Try Ca  Sr

Valance electrons and e- dot  Valance electrons are those in the outermost shell  Total no more than 8  Last set of s and p electrons only  Only electrons that react in chemical reactions  Can identify by rows!!!

Electron dot notation  Use valance electron count, draw dots!  Only 8! Go one top, bottom, left, right, then repeat as needed.   Hor Mg Ne 