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UNIVERSITY OF MEMPHIS / Chemistry / CHEM 1110 / Why is directly observing electrons impossible?

Why is directly observing electrons impossible?

Why is directly observing electrons impossible?

Description

School: University of Memphis
Department: Chemistry
Course: General Chemistry I Lecture
Professor: Henry kurtz
Term: Fall 2018
Tags: Chemistry, chapter2, KenshaClark, Clark, UniversityofMemphis, and Chem1110
Cost: 25
Name: Chemistry Chapter 2 Notes
Description: These notes cover the concepts and equations in Chapter 2
Uploaded: 09/23/2018
3 Pages 37 Views 5 Unlocks
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CHAPTER 2: THE QUANTUM MECHANICAL


Why is directly observing electrons impossible?



MODEL OF AN ATOM

Quantum mechanles was developed to explain the behavior of these ting particles pilatori particles benave much differently than manu scopie partides (element es molecules

Under some conditions they behave like partices, sometimes behave like waves. * Directly observing electrons is impossible because it changes its benavor


What happens to waves in the event of destructive interference?



Much of an atomis behavior comes from the electrons.

The bare properties of an electron give matter its behavior -Wave Fundamentals We also discuss several other topics like What are the three categories of managerial roles according to mintzberg?

crest

amplitude -

wavelength is t in nm trough

amplitude is vertical distance from midline wavelength

to prest of trough Frequency (v) is of waves that pass through a particular paint in 1 second


Are frequency and wavelength inversely proportional?



Don't forget about the age old question of How do ocean basins form?

(Hz= 1 cycles) speed of a wave is Rum • WHz

• Wave interference

WAVE DIFFRACTION PARTICLES DONT Constructive Interference - amplitude gets larger when two in phase DIFFRACT

waves combine (ex. everyone yells at once, and its loud) Destructive interference - two out-of-phase waves cancel each other out We also discuss several other topics like Where atmospheric pressure came from?
If you want to learn more check out What is the study of human history through excavation and analysis of artifacts and other remains present?

- ex. you're in a crowded room and can't hear

what your friend is saying to Electromagnetic radiation - emission and transmission of energy Don't forget about the age old question of What is socio-centric?

• Bladebody radiatisa when heated, e oscillate, electromagnetic radiation released Value of the speed of light (a type of electromagnetic radiation) - 3.0x 108 mis (in a vacuum We also discuss several other topics like What are the five principles of politics?

- use the symbol a Ware Nature of Light

different wavelengths = different colors - different anplitudes different brightness

the color you see is the opposite of the color being absorbed "White light is a mixture of all colors of visible light - red has longest ł, violet has the shortest highest energy

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Frequency and wavelength are inversely proportional

RADIO WAVES

MICROWAVES

INFRAREN LIGHT

LONGER

LOWER ENERGY SHORTER I VISIBLE LIGHT IHIGHER ENERGY

ULTRA VIOLET

ne X-RAY

& GAMMA RAYS / Cosmic RAYS t

• Wavelength frequency - Speed of light

AP=C (-3.0*100 ms. - C is constant, so if you know torr you can calculate the other THE ELECTROMAGNETIC SPECTRUM

•Definition the range of wavelengths of all possible

electromagnetic radiation to

•Short a= high / high energy on staan of dust

long n= low "Gamma Rays-highest energy dangerous to humanshaha

no ex. sun, stars i X - Baus- have medical uses a

-can be harmful in large amounts on a W Radiation cause of sunburns

• Visible light violet (shortest 1) to red Clongest )

o not enough energy to damage humans Infrared emitted by warm objects in

• Microwaves- radars and microwave ovens alla hora

i - easily absorbed by Hao out to - Radio Waves transmit signals VOM

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2.3 ATOMIC SPECTROSCOPY AND THE

BOHR MODEL "Atomic Spectroscopy the study of electromagnetic radiation

. emitted / absorbed by atoms - ATOMIC SPECTRA

atoms absorbenergy and emit it as light.

- different elements are different coler lights emission spectrum - series of bright lines fermed by passing light

emitted by an element through a prism - can be used to identify an element

the white light spectrum is continuous

Clooks like a long rainbow rectangle)

- spectra of elements are bright lines with dark between -Rydberg equation - predicts of hydrogen emission spectrum

n a Rita R= (1.097x10 m)

T = R(ma na) min are integers THE BOHR MODEL 2

• Niels Bohr- Danish physicist nu

Dom - tried to create a model for the atom that explained

atomic spectra J -stationary states - electrons erbits at fixed distances from nucleus

- proposed electrons only produce radiation when

- moving between stationary states

• electrons are never observed between States

•stationary states are only at fixed positions

- - this is why enission spectrums are made of lines the energy produced by an electrons transition is the difference between the states it transferred between

smaller transition less energy Atomie SPECTROSCOPY AND THE IDENTICATION OP ELEMENTS EMISSION SPECTRUMS ARE LIKE AN ELEMENTS BARCODE

flame test can identify elenents in compound by color of flane

• absorption spectrum - dark lines an bright background

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emission - transition from high low energy level

• absorption - how high energy level

2.4 THE WAVE NATURE OF MATTER

THE DE BROGUE WAVELENGTH, THE UNCERTAINTY PRINCIPLE

AND INDETERMINANCY Wave Nature of the Election ;

-REPLACED BOHR'S MODEL - proposed by Louis de Broglie - evidenced by Davisson - Germer experiment

in which é were diffracted by a metal

crystal in a wave pattern of interference

o-pattern caused by é interfering with themselves

• The wave nature is a property of each é itself, not only groups

• Ware nature explains stationary states and how é do not I crash into the nucleus.

THE DE BROGLIE A

shorter t = higher kinetic energy

• de Broglie relation

as a h/my otros n = ware length of electron h= Planck's constant = 6.626*10 34 5 mo mass of e-

v = velocity THE UNCERTAINTY PRINCIPLE

•We cannot observe wave and particle nature of t at the

same time complementary properties the more you know about one,

the less you know of the other

- ex. particle ware nature of e velocity of e has to do with wave nature. position has to do with partiele nature we cannet measure positin + velocity at the same time to

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Heisenberg's Uncertainty Principle

axomavah AX= uncertainty in position Av = uncertainty in velocity m = mass of e

n = Planck's constant

• Ax and av are inversely proportionate

the more accurate one is, the less accurate the other INTERDETERMINACY AND PROBABILITY DISTRIBUTION

MAPS

trajectory- path

lo- can be predicted based on position and velocity oble we cannot knew position AND velocity of electron, we

I can't determine its path probability distributico map statistical map suderi

2-shows likely location of election CLASSICAL TRAJECTORY QUANTUM MECHANICAL PROBABILITY

DISTRIBUTION MAP

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indeterminancy- present circumstances do not determine future

in quantum - Mechanics 2.5 QUANTUM MECHANICS AND THE

ORBIT +extra class petes CLASS ACTES

• "W catastrophe

-nolates law of conservation of energy - Max Planck said electromagnetic energy can goly be released in

quantized fermo s

I h = 6.626*10 TS Erhv e-energy h-Plandis constant (artoo oo wo has Photoelectric effect frequency of light for which en begin to eject from surface

so is independent of the intensity of light

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The particle nature of light

tight energy quantized into protons

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- hvis energy of a photon - threshold energy reached when huo

& is energy to remove è from surface a bean of light is not just a wave, its a shower of particles called

photonics

*

Pesition and enesey are complenertary properties like position and velexity * Electrons positions are described by orbitals

Srbital - probability distributian map used to describe likely position of és Distribution of é is important to chemical bonding trogen Schrodinger Equation - CAN ONLY BE SOLUED FOR HO ATOM

Hύν H Hamiltonian operator Preprosto 2020 perano operator is like a set of instructions E = actual energy of é as y = wave function - function that describes wave like nature of e SOLUTIONS TO THE SCHRÖDINGER EQUATION FOR THE HYDROGEN ATOM Quantum numbers interrelated is represent shapelenergy cof orbitals

lon-prinapal quartum #always an integer

- determines orbital's size tenergy -menanze qurtunts 2

- higher n= higher energy

- highern = more space between é and nudeus w Ex Hydrogen atoms in

En = -2, 18 x 10185 (52) n = 1, 2, 3 ...

- Ey-1.36410-145 - Ez = -2,42% 10th J * As 'n increases,

E = -5,45 x 10145 the spacing between Loomuha

s energy levels as

a decreases to n=1

,2-2, 18* 10 J if

for test

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n=3

n=2

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Energy

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*max values 2. The Angular Momentum Quantum (1) 12=n-1 2022 (11)

integer - determines shape of orbital I VALUE OF L I LETTER DESIGNATION

2=0 (spherical)

listed lina.b

notes/

SUP 1=3 1=4

I beyond 3 are ~ 2=5

18 in alphabetic order 1=6,789.00

indikilen starting with a -If n 3, the possible values of 2 (n-1) are 0, 1, and a

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B. The Magnetic Quantum (mi)

- integer

represents Orientatica of orbital - values of M, possible are 12 m, 2+2

ex. 20 m, o

1-1, mis hoit 1-2 M = -2,-1,0, +1, + 2

4. Spin Quantum (ms)

- orientation of the spin of e -election spin-property of an e

- alle have the same ant. cf spin -2 options for spin SPIN UP

SPIN DOWN Mgt / 2

Mg -

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Each combo of nih, and m, specifies are atomic orbital ex. n = 1, 2-0, m, 20 is the 1s orbital

(1 is value of n s specifies 2:0)

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principal level / principal shell-group of orbitals with same ! * Sublevel /subshell-orbitals with same n and ?

The # of sublevels in any level = n .

• # of orbitals in sublevel = 27+1 .# of orbitals in levet na nad

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PRINCIPAL LEVEL (2)

SUBLEVEL (2)

N=3

1-0 1-

2-2 35 orbital 3p orbitals | 3d orbitals m = 0 lm = -hoitho=-2,-1, G +1, +2

2-0 L =Late asorbital ap orbitals. m = 0 Ima -1, 0, +1

n=1

2-0 Is orbital

M = 0

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Atomic Spectroscopy EXPLAINED

•When an atom absorbs energy, an e moves to a higher energy cobital her - This isn't stable, so atom "relaxes back to lower Orbital at - Atan relaxing releases a light photer whose energy is equal to

the difference between ar bitals Energy of orbital = En = -2,18* 16-18 J (2) nprina quant # A E = Efinat - Einitial

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ENERGY

Excitanan AMD RADIATION n=3

my 2. Light enitted, n=

21

é relates to to e absorbs energy,

- lower energy level is excited to unstable

level

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AE: -2.18x108J Gazon e Atatom - Ephoton enitted in

no final state Irelaxed stale ne initial state excited state

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2.0 THE SHAPE OF ATOMIC ORBITALS

•Shapes of orbitals determine the shape of the molecule sorbital

based on how they overlap Shape of orbital comes mainly from 2 s al sorbital (2-0)-spherically symmetrical I "probability density probability (per unit volume) of finding

the é at a certain point

-expressed as 3D plot of function ya a probability density probability unit velame ridistance from nucleus

V decreases as r increases

• radial distribution function

function represents likelihood of finding é within a spherical shell a certain distance (r) from the

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total radial probabilite probabilite nucleus

I unstvolum & volume of shell at

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•radial distribution represents probability @ a radius, not one point

- Always has value of o @ nucleus'

node a point where & (wave function) and ye (probability

. density) both hit o - probability of ě being at a node is on

-nodal planes are all destructive interference op orbitals (2=1)

"not spherically symmetrical, have a lobes on sides of nucleus - the 3 p orbitals (m, -7,0,+1) are perpendicular to one another

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d orbitals (2-2)

- 5 orbitals (m. = -2,-1, 6, +1, +2) - All 5 EXCEPT dz2 are clover leaf shaped ?

dz? has a lobes, and donut shape along xy planet - dxy (xy plane), dxz (x2 plane), dyz Cyz plane) dy2y2 - four lobes en x and y axes I

•f orbitals (2-3)

-seven erbitals (m=-3, 2, 1, 0, +1, +2, +3)

more lobes + hodes than other orbitals

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THE PHASE OF ORBITALS

orbitals are 30 waves

•phase the sign of the amplitude of waves

1D WAVĚ PHASESI

130 WAVE PHASES! Is orbital 2p orbital

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