4-1 RADIANT ENERGY 4-2 QUANTUM THEORY 4-3 ANOTHER LOOK AT THE ATOM 4-4 A NEW APPROACH TO THE ATOM...

4-1 RADIANT ENERGY 4-2 QUANTUM THEORY 4-3 ANOTHER LOOK AT THE ATOM 4-4 A NEW APPROACH TO THE ATOM 4-5 ELECTRON CONFIGURATIONS Chapter 4 Electron Configurations

What do you see?

HAVING SEVERAL DIFFERENT IMAGES W/IN ONE IS AS CONFUSING AS THE MYSTERY OF ELECTRONS WERE TO THE SCIENTISTS. THERE WAS NO WAY TO SEE THEM BUT THEY KNEW THE ELECTRONS MUST BE THERE SCIENTISTS JUST DIDNT KNOW WHAT TO DO ABOUT THEM OR WHAT THEY SPECIFICALLY DID

WHAT ARE THE 4 CHARACTERISTICS OF AN ELECTROMAGNETIC WAVE? WHAT ARE THE MAJOR REGIONS OF THE ELECTROMAGNETIC SPECTRUM? 4-1 Radiant Energy

Light Most of what we know about how e- behave in atoms was learned from watching how light interacts w/ matter Light travels through space and is a form of radiant nrg

Nature of Light The properties of light: Properties of wave Properties of particles

Waves Light travels in waves like the ocean These waves are electromagnetic wh. makes light a form of electromagnetic radiation Electromagnetic radiation (x-rays, gamma rays, radio waves) Electromagnetic waves have electric and magnetic fields oscillating at right angles to each other and to the direction of the motion of the wave

Waves All waves can be described by 4 characteristics Amplitude Wavelength Frequency speed

Amplitude The height of the wave Determines the brightness/intensity

Wavelength Distance b/w wave crests The distance it takes for the wave to make 1 cycle Visible light has a wavelength b/w 400-750 nanometers

Frequency Tells how fast the wave oscillates up and down Measures how many cycles a wave makes in 1 second Units: 1/s, s -1, 1 Hz Radio stations broadcast at megahertz 97.5 FM means the frequency of those radio waves are moving at 97.5 x 10 6 cycles per second Visible light moves b/w 4 x 10 14 7 x 10 14 s -1

Speed of light No matter the wavelength light moves at 3.00 x 10 8 m/s b/c the speed does not change, relationships b/w wavelength and frequency can be made The shorter the distance b/w the crests of a wave, the faster the wave oscillates up and down The shorter the wavelength, the greater the frequency

= c/ : wavelength c : speed of light 3.00 x 10 8 : frequency If given the frequency of 4.74 x 10 14 s -1, what would the wavelength be?

Electromagnetic Spectrum

Types of waves: Infrared

Types of waves: x-rays

WHAT IS MEANT BY NRG QUANTIZATION? HOW IS THE NRG OF RADIATION RELATED TO ITS WAVELENGTH? HOW DOES THE IDEA OF PHOTONS OF LIGHT EXPLAIN THE PHOTOELECTRIC EFFECT? 4-2 Quantum Theory

???Unanswered questions??? Why would metal radiate different wavelengths at different temperatures? Start heating, no visible light Starts to glow red White hot Why do different elements have different colors?

Plancks Theory Max Planck (1858-1947) Proposed that there is a fundamental restriction on the amounts of nrg that an object emits/absorbs Called these pieces of nrg quantum

Plancks Theory Quantum/quanta Fixed amount Goes against the previous theories of nrg

Plancks Theory E = h E = energy h = 6.626 x 10 -34 J-s Unit: joule-second = frequency

Plancks Theory Using Plancks theory, scientists can determine the temp of distant planets by measuring the of the electromagnetic radiation they emit

Plancks Theory Energies absorbed/emitted by atoms are quantized Means their values are restricted to certain quantities What would happen if a cars nrg was quantized? A car can only go so fast

Plancks Theory Look at figure 4-11 on pg 132 In which direction would a person walk on the ramp/stairs to increase her potential nrg? Up the ramp/stairs Is there any location on the ramp that cant be occupied during this increase? No How does a persons movement on the stairs compare to a similar movement on the ramp? To climb the stairs, a person can only occupy distinct levels/stairs Would the motion of an elevator be continuous/not? Explain. Yes, the motion is continuous, but people can only get off at certain levels.

Photoelectric Effect Albert Einstein (1879-1955) When light of a certain frequency is shone on some metals, the electrons of that metal will be emitted from the surface These emitted e- are filled with nrg and can be used thereafter Solar calculators Camera light meters Each metal has a minimum frequency of light to release e- Example: sodium metal is not affected by red light no matter its intensity. A very faint violet light however will cause the e- to be emitted

Photoelectric Effect Photons Particles of EM radiation No mass Carry a quantum of nrg nrg has certain minimum to cause ejection of photoelectron Photons nrg must equal or exceed nrg needed to free an e- from an atom nrg depends on frequency E photon = hv

Photoelectric Effect Photon strikes surface of metal Photon transfers nrg to e- in metal atom e- chooses to swallow whole photon If swallowed, e- will use nrg to jump off the atom The important, deciding factor is the of the photon not the # of photons So why does violet light release e- but not red? Violet has a greater , therefore a greater amount of nrg/photon

Photoelectric Effect nrg of a photon explains effects of different kinds of EM radiation Hospitals have signs warning that x-rays are being used X-rays have high which means high nrg photons wh. could cause harm to living organisms Radio waves surround us w/o any warning signs Low , low nrg photons wh. dont harm organisms.

READ THE CHEMISTRY IN ACTION BOX ON PAGE 132 Photoelectric Cells

4-2 Section Review p 134 (1-4) What does it mean to say that nrg is quantized? The nrg emitted/absorbed by any object is restricted to fixed amounts called quanta How is the nrg of a quantum of radiant nrg related to its frequency? The higher the frequency of light, the greater the nrg/photon Why do you not ordinarily observe the quantization of nrg in the world around you? Ea quantum of nrg is too small to notice in the everyday world People who work around x-rays often wear film badges to monitor the amount of radiation to which they are exposed. Why do x-rays expose the film in the badge when other kinds of electromagnetic radiation do not? X-rays have high frequencies. X-ray quanta have enough nrg to expose the film, whereas lower frequency waves do not.

HTTP://WWW.YOUTUBE.COM/WATCH?V=_5F 34NFWVL4 Recap Video

Group Activity Each group will read their article A PowerPoint will be made of the article information The PowerPoint needs: At least 5 slides At least 2 pictures/diagrams All members of the group presents

WHAT IS A LINE SPECTRUM? HOW DOES THE BOHR MODEL EXPLAIN THE LINE SPECTRUM OF HYDROGEN? 4-3 Another Look at the Atom

Line Spectra A spectrum that only contains certain colors/wavelengths Also called the atomic emission spectrum A fingerprint of that particular element Ea. element has its own color Sodium had a yellow color in your flame test

Atomic Emission Spectra The set of frequencies of EM waves emitted by atoms of a particular element Explains neon signs Each element has a unique spectrum and therefore can be identified within an unknown such as through a flame test Your lab last Monday

Atomic Emission Spectrum Not every color of the spectrum seen in an emission spectrum b/c not all frequencies of light are emitted Photo courtesy NASA Hydrogen spectrum Photo courtesy NASA Helium spectrum

Why does it take more nrg for the painter to climb to the top rung of the ladder? The electrons of an atom occupy orbitals around the atoms nucleus that are similar to the rungs of a ladder. Why does the paintbrush hit the ground with more energy when it falls from the top rung? The painter is moving farther away from Earths surface climbing to the top rung. The paintbrush had more potential energy at the top of the ladder. Also, it takes energy for an electron to move from an orbital close to the atoms nucleus to an orbital farther from the nucleus, just as it takes energy to move up the rungs of a ladder. For example, just as a person cannot step between the rungs of a ladder, an electron cannot occupy the space between the atoms orbitals.

The Bohr Model of the Hydrogen Atom Niels Bohr (1885-1962) Attended lecture of Rutherford and used his, Planck, and Einsteins theories Focused on Hydrogen Simplest w/ only 1 e - Using Rutherfords planetary orbit model of e - around the nucleus, Bohr said that ea. orbit specified a certain quantum of nrg

The Bohr Model of the Hydrogen Atom Bohr labeled ea. nrg level (orbit) w/ a quantum #, n The lowest nrg level (closest to nucleus), called ground state n = 1 When the e- absorbs the right amount, it jumps to a higher nrg level Called an excited state Quantum #s: n=2, n=3, n=4, etc Excited states represent larger orbits farther from the nucleus

The Bohr Model of the Hydrogen Atom

Physics 2000 http://www.colorado.edu/physics/2000/quantumzone/ bohr.html http://www.colorado.edu/physics/2000/quantumzone/ bohr.html

Matter Waves Movement of e - We draw the orbitals as circles but the e- dont actually move in a circle around the nucleus e- move around as waves Discovered by Louis de Broglie 1924 Physicist French graduate student

Heisenbergs Uncertainty Principle If I put a balloon into a completely dark room, could you locate it without moving the balloon? It is nearly impossible Every time you touch the balloon it moves! The e- is just like this

Heisenbergs Uncertainty Principle Cont. What if we put that same balloon in the dark room and gave you a flash light? Would you be able to find it now? Yes, the tiny photons from the light reflect off the balloon & back into your eyes so that you see the balloon w/o having to touch it

Heisenbergs Uncertainty Principle Cont. When you hit the balloon w/ the photons, the balloon is so much bigger than the photons When you hit an e- with a photon, the photon is the same size as the e- so they reflect off one another After the collision the e- is now going in a different direction and is usually going much faster than before

Heisenbergs Uncertainty Principle States that there is no way to know exactly what an e- position and speed of an e- at any given time

Lasers Read the Chemistry in Action on p 140

4-3 Section Review 1. What is the difference b/w a line spectrum and a continuous spectrum? 1. Line spectrum contains only certain colors/wavelengths. Continuous spectrum contains all colors, wh. Fade gradually into ea. other 2. How does the Bohr model account for the line spectrum of the hydrogen atom? 1. The Bohr model labels the different nrg levels wh. Can be occupied by an e-. The e- absorbs/emits a certain quantity of nrg when it moves b/w these nrg levels. The frequencies in the line spectrum of hydrogen correspond to the quantity of nrg emitted when an e- moves from a higher to lower state. 3. What is Heisenbergs Uncertainty Principle? 1. States the position and momentum of a moving object cant simultaneously be measured and known exactly 4. You have learned that in attempting to locate an e-. The act of measurement changes the system. Suppose that you measure the temp. of a cup of hot tea with a cold thermometer. How does the use of the cold thermometer affect the temp reading? Is this an example of the uncertainty principle? Explain.

WHAT IS AN ATOMIC ORBITAL? HOW DO THE S, P, D, AND F ORBITALS COMPARE IN SIZE, SHAPE, AND ENERGY? 4-4 A New Approach to the Atom

Quantum Mechanical Model Model of the atom Explains properties of the atom by treating electrons as waves that have quantized their energies Though unable to tell exactly where an electron is or how it is moving Model does describe probability that electrons will be found in certain locations around the nucleus

Probability and Orbitals Electrons are seen in a blurry cloud or negative charge electron cloud More dense the area, the more probable to find electrons Electron density: density of an electron cloud High probability high electron density Low probability low electron density

Probability and Orbitals The probability of finding electrons in certain regions of an atom is described by orbitals An atomic orbital is a region around the nucleus of an atom where an electron with a given energy is likely to be found Orbitals have characteristic shapes, sizes, and energies

Probability and Orbitals 4 kinds of orbitals s, p, d, and f s orbital Circle shaped Increase in size w/ ea. increase in nrg level p orbital Dumbbell/figure eight shaped d orbital No definite shape f orbital No definite shape

Orbitals and Energy Bohr suggested energies in electrons were quantized These quantizations labeled as principle quantum levels designated by quantum #, n Quantum Mechanical Model adds sublevels to these principle quantum levels Sublevels have a pattern # of sublevels equals the quantum # n = 1 1 sublevel n = 2 2 sublevels, etc

Orbitals and Energy

Just like an address You have a name, street, city, state, and zipcode An electron has its principal energy level, the sublevel, and its orbital within that sublevel First energy level n = 1 One sublevel s Called the 1s sublevel and 1s orbital

Orbitals and Energy Second energy level n = 2 2 sublevels 2s slightly larger than 1s 2p consists of 3 orbitals (p x, p y, p z ) x, y, & z stand for axis (3D)

Orbitals and Energy 3 rd principle energy level n = 3 3 sublevels 3s 3p 3d five orbitals

Orbitals and Energy 4 th principal energy level n = 4 4 sublevels 4s 4p 4d 4f 7 orbitals

Electron Spin Electrons spin either clockwise or counterclockwise Each orbit has 2 electrons Each electron will have an opposite spin Represented as arrows

4-4 Review (p 146 1-4) What is an atomic orbital? An electron orbit? Sketch the general shape of an s orbital and of a p orbital. List the kinds of sublevels in the fourth principal energy level of an atom. How many electron can be found in any orbital of an atom? Are their spins parallel or opposite?

Ground-State e- Configuration Atoms want all their e- in a pattern and where they are supposed to be (organized) When an atom has a lot of e-, they want them in the lowest nrg levels as possible

Aufbau Principle All sublevels of an nrg level have equal nrg For example, in the 2p sublevel, the 2p x, 2p y, and 2p z orbitals are all equal in size An f sublevel has more nrg than a d orbital, wh. has more nrg than a p, wh. has more nrg than an s For example, a 2p is larger than a 2s

Aufbau Cont It is possible for sublevels in one nrg level to overlap sublevels in another nrg level For example, looking at nrg, a 4s orbital would be smaller than a 3d orbital We would normally think they would go in order

Pauli Exclusion Principle There are two e- in ea. orbital ea. one has a different spin to it. A 2s orbital would have 2 e- in it A 2p orbital would have 2 e- in ea. of its orbitals (x, y, and z) These different spins, mean one is spinning clockwise and the other counterclockwise.

Hunds Rule For ea. orbital in a sublevel (s, p, d, or f) will need special placement of the e- There are 2 e- in ea. orbital, for however many orbital you have w/in a sublevel (1 for s, 3 for p, etc), you will need to place e- with the same spin in first and then add the others Lets look at some examples

Hunds Rule 1. 2.3. 4.5.6.

Orbital Diagrams A way to represent the e- in an atom Lets you see the different spins in an orbital What does it look like? Empty box empty orbital Single up arrow orbital w/ 1 e- Up and down arrow orbital w/ 2 e-

Orbital Diagrams Cont. Lets look at Carbon When we look at the periodic table, Carbon has an atomic # of 6 we know that means there are also 6 e- Lets put them in our boxes, but put them in order of orbitals 1s2s2p

Orbital Diagrams With a partner, draw the orbital diagrams for Helium, Oxygen, and Fluorine

Electron Configuration Notation Another way to represent the e- in an atom Instead of drawing boxes, you make a list For our Carbon example, we had 6 e- total 1s 2 2s 2 2p 2 We have a chart we can use to let us know which orbitals to place in our list firstchart

e- configurations With your partner, write the e- configurations of Helium, Oxygen, and Fluorine.

4-1 RADIANT ENERGY 4-2 QUANTUM THEORY 4-3 ANOTHER LOOK AT THE ATOM 4-4 A NEW APPROACH TO THE ATOM...

Documents

Transcript of 4-1 RADIANT ENERGY 4-2 QUANTUM THEORY 4-3 ANOTHER LOOK AT THE ATOM 4-4 A NEW APPROACH TO THE ATOM...