Neutron diffraction is the application of neutron scattering to the determination of atomic/ magnetic structure of a material. The technique is similar to XRD but the different type of radiation gives complementary radiation. It is of different types and overcomes the demerit of XRD. It has a lot of applications such as structure determination, locating light atoms, magnetic properties study, study of atomic vibration and other excitations.
Neutron diffraction is the application of neutron scattering to the determination of atomic/ magnetic structure of a material. The technique is similar to XRD but the different type of radiation gives complementary radiation. It is of different types and overcomes the demerit of XRD. It has a lot of applications such as structure determination, locating light atoms, magnetic properties study, study of atomic vibration and other excitations.
The splitting of the main spectral line into two or more components with a slight variation in wavelength in the magnetic field is called fine structure in spectroscopy. It means that, in the magnetic field, the electron energy splits to give its sub-states. The electron transitions from these substituent energy levels give additional spectral lines. These are known as fine structures of the main spectral line. The hydrogen spectrum exhibiting the fine structured lines is known as the hydrogen fine spectrum.
For more information on this topic, kindly visit our blog article at;
https://jayamchemistrylearners.blogspot.com/2022/04/fine-structure-of-hydrogen-atom.html
The splitting of the main spectral line into two or more components with a slight variation in wavelength in the magnetic field is called fine structure in spectroscopy. It means that, in the magnetic field, the electron energy splits to give its sub-states. The electron transitions from these substituent energy levels give additional spectral lines. These are known as fine structures of the main spectral line. The hydrogen spectrum exhibiting the fine structured lines is known as the hydrogen fine spectrum.
For more information on this topic, kindly visit our blog article at;
https://jayamchemistrylearners.blogspot.com/2022/04/fine-structure-of-hydrogen-atom.html
Introduction to the structure of atoms from the view of a chemist - what are neutrons protons and electrons and how are they organized ? How are electrons organized - in 3 quantum numbers. Experimental evidence from the Bohr model.
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ArgusLab is a very powerful program that can be installed on a Windows PC. You can model even big molecules, create 3D geometry optimized models and calculate various properties like dipolmoments and HOMO/LUMO energies and shapes.
Really useful for chemical education.
Properties of coordination compounds part 1Chris Sonntag
Present a short review about Crystal field theory and how we can use the results of it to explain various physico-chemical properties of transition metal complexes.
How do we describe the bonding between transition metal (ions) and their ligands (like water, ammonia, CO etc) ?
The Crystal Field Model gives a simple theory to explain electronic spectra.
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Description of the basic steps in catalysis
Discussion of oxidation addition, reductive elimination and migration reactions with examples
Catalytic cycles
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The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
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3. REVIEW LESSON 1
Atomic nucleus
atomic mass unit amu
Isotopes / MS
Bohr model of the Hydrogen atom
absorption and emission spectra
<-> energy levels in the atom = orbits
Electron as standing wave
deBroglie: λ = h/p = h/(mv)
Schroedinger eq. for 3D el.waves
=> 3 quantum numbers n, l and m
Aufbau principle
Shielding of electrons
4. ATOMIC SPECTRA
Show us the energy levels in an
atom/molecle (n) and also splitting (l)
5. MAIN ENERGY LEVELS (N)
Each line with a wavelength λ corresponds to
an electron transition with an energy
∆E = E2 – E1 = h * c / λ 1/ λ = ν
wavenumber in cm-1
Planck constant h = 6.626 x 10-34 J s
C speed of light = 300’000 km/s
6. Energy unit “electronVolt” eV
= energy of 1 electron in a field of 1 V
1 eV => λ = 1240 nm
λ = 1240 nm / E [eV]
7. CHECK
Which light will an electron emit, when it
falls from energy level 4 to 2 ?
(is it shorter or longer than from 4 to 3 ?)
Which energy in eV will an electron bring from
its ground level to the first excited state ?
8. WHY ONLY CERTAIN ENERGY LEVELS ?
The Bohr model cannot explain why
electrons can only live in certain orbits !
When we look at electrons as WAVES, we
can understand that each orbit must be a
mulitple of λ/2
9. CLASSICAL VS. QUANTUM MECHANICS
Quantum
mechanics
describes the
function
which
represents
these waves
12. FROM LINE SPECTRA TO WAVEFUNCTIONS
(ORBITALS)
Model the electron as a standing wave in
3D, we can describe the most likely places of
an electron and its energy from the
Schroedinger Equation
If you want to know this in detail:
http://www.youtube.com/watch?v=7LBPXP09KC4
and:
http://www.physicsforidiots.com/quantum.html
This equation leads to 3 quantum numbers
which describe the energy and the
distribution of the electron in an atom
13. QUICK OVERVIEW ABOUT SCHROEDINGER EQ.
From: http://www.youtube.com/watch?v=cdaIsu4jBtA
26. 3 RULES FOR CONFIGURATIONS
Aufbau Principle:
Electrons are filled according to their
lowest energy possible
Pauli exclusion principle:
Electrons must differ in one of 4 quantum
numbers
=> max 2 electrons in one orbital
Hund’s Rules:
Electrons want to have maximum SPIN
30. FINE STRUCTURE OF HYDROGEN SPECTRA
When an electron is in an orbital, it can
cause different energies because of 2 forces:
• SPIN
• ANGULAR MOMENTUM
31. 3 MOMENTUMS: SPIN, ANGULAR AND SUM
Watch clip until t=6:20 mins
http://www.youtube.com/watch?v=V7DcOXbVY70
32. ELECTRON HAS 3 “MOMENTUMS”
An electron rotates around itself (like the
earth) producing a SPIN S
This produces
a magnetic field
around the
electron
33. ANGULAR MOMENTUM L
Because the electron circles around the
nucleus, it creates an angular momentum
( L ) – which creates also a magnetic field
Since only certain
radius are possible, L
can have only discrete
values
34. SPIN-ORBIT COUPLING J
Both momentums
combine to the
“total angular momentum” J
Lower
energy !
36. CONSEQUENCE
An electron in an s-orbital has angular
momentum of zero on average (L=0)
An electron in a p orbital can have 2
different energies:
depending if the spin momentum points
in the same direction of the angular
momentum or opposite.
A smaller J (L-S) means lower energy
than higher J (L+S)
37. TERM SYMBOLS (RUSELL-SAUNDER)
To describe the electron configuration in
an atom:
2S+1LJ
L: orbital of the electrons
(S =0, P =1, D =2, F =3)
S: total spin of all these electrons
J = L+S, L+S-1, L+S-2, ....|L-S|
Orbital angular
momentum
multiplicity
Total angular
momentum
46. 3 “NEW” QUANTUM NUMBERS
(1) Angular Momentum L
= the unfilled highest shell of the electron(s)
Add l of each electron in this shell:
l1 + l2 , …. , |l1 - l2| (min.0)
Example: 2 electrons in p shell:
L = (1+1 ) 2 -> 1 -> 0
50. ENERGY ORDER
Apply Hund’s rules to find the lowest energy
ground state:
1. Term with highest S
2. Within the same S, the term with highest L
3. Within same S and L:
a) shell half-filled or less: lowest J
b) more than half-filled: highest J
(for excited states, we cannot get the lowest
energy from these rules)
51. EXAMPLE C ATOM GROUND STATE
2 p electrons with max. L in a
configuration with highest spin S=1
=> L=1 (“P”)
=> J = 2,1,0
Less than half-filled => lowest J:
=> ground state: S=1, L=1, J=0: 3P0
52. EXAMPLE C ATOM EXCITED STATE
Configuration : 2 p1 and 3 s1
Spin: +1/2 +1/2 or +1/2 -1/2 => S= 0,1
1 electron in s orbital => l1 = 0
and 1 el. in p orbital => l2 = 1
=> L= 1+0, 1-0 = 1 (“P”)
=> S=0: J=1
S=1: J = 2,1,0
Possible states:
1P1 and 3P0, 3P1, 3P2
54. EXAMPLE FE ATOM
Configuration 4s2 3d6
(1) Spin: 2
(2) L: -2, -1, 0, 1, 2
the max.L is in this state: L=2
(-2 -1 +0 +1 +2 +2)
(3) J: 4,3,2,1,0
Hund’s rule: max. spin, L=2 (“D”)
highest J (more than half-filled): 4
=> Ground state: 5D4
55. HOMEWORK (1)
1. Ground state conf. for He
2. Excited state (a) 1s1 2s1
3. Excited state (b) 1s1 2p1
4. Ground state conf. for Be 2s2
5. Excited state 2s1 2p1