The document discusses the oxidation states of lanthanides. It states that:
1) All lanthanides most commonly exhibit a +3 oxidation state, but some can also be +2, +4, or lower states depending on electronic configuration.
2) The most stable oxidation state is generally +3 due to the strong attraction of the 4f electrons to the nucleus.
3) Elements in other oxidation states act as strong reducing or oxidizing agents as they try to attain the +3 state.
Introductory PPT on Metal Carbonyls having its' classification,structure and applications.This is a basic level PPT specially prepared for UG/PG Chemistry students.
A brief introduction to lanthanide elements is given.
Order .ppts like this at <https://www.fiverr.com/anikmal/teamup-with-you-to-prepare-the-best-presentation>
Along with their physical and chemical properties are also shown. Helpful for quick understanding on lanthanide series.
Introductory PPT on Metal Carbonyls having its' classification,structure and applications.This is a basic level PPT specially prepared for UG/PG Chemistry students.
A brief introduction to lanthanide elements is given.
Order .ppts like this at <https://www.fiverr.com/anikmal/teamup-with-you-to-prepare-the-best-presentation>
Along with their physical and chemical properties are also shown. Helpful for quick understanding on lanthanide series.
Quantum yield, experimental arrangement, reasons for high and low Quantum yield, problems, photochemical reactions, kinetics of photochemical decomposition of HI, photosensitized reaction, mechanism of photosensitization,
Labile & inert and substitution reactions in octahedral complexesEinstein kannan
The first part includes a definition of labile and inert. lability and inertness on the basis of VB theory and CFT and also factors affecting inertness and lability of the complexes.
And also the second part includes Substitution Reactions in Octahedral Complexes like mechanisms and their evidence.
Quantum yield, experimental arrangement, reasons for high and low Quantum yield, problems, photochemical reactions, kinetics of photochemical decomposition of HI, photosensitized reaction, mechanism of photosensitization,
Labile & inert and substitution reactions in octahedral complexesEinstein kannan
The first part includes a definition of labile and inert. lability and inertness on the basis of VB theory and CFT and also factors affecting inertness and lability of the complexes.
And also the second part includes Substitution Reactions in Octahedral Complexes like mechanisms and their evidence.
Inner Transition Element by Dr.N.H.BansodNitin Bansod
Inner Transition Element, electronic configuration lanthanide and actinide, lanthanide contraction & consequences, oxidation state, magnetic properties, ion-exchange method for separation, similarities, and differences of lanthanide and actinide
The bonding in lanthanide complexes differs from that seen in transiti.docxchrisflorence13710
The bonding in lanthanide complexes differs from that seen in transition metal complexes. Discuss how this difference in bonding explains why for a transition metal ion, such as Co3+, the colour of its complexes varies depending on the co-ordinated ligands, whilst all complexes of a particular lanthanide ion, such as Eu3+, exhibit a similar colour (b)
Solution
Lanthanides (inner transition metals) resemble 3d transition metals mainly in forming coloured complexes.
But they differ in the oxidation state which is due to large reduction potential for oxidation state when related to 1 electron reduction in case transition compounds.
There is a lack in 4f chemistry of very high oxidation state is familiar to 3d transition complexes. The 4f metals are not willing to form strong Ln = O double bond complexes and lack of significant third ionization energy IE 3 is important in maintaining +3 oxidation state at the end of the lanthanide series.
The increase in atomic radius is greater than between 3d and 4d metals than between the 4d and 5d metals because of lanthanide contraction.
Sigma bonding interaction in coordination compound is due to attraction of electrons on the ligand for the charge of metal ion.
Electrons in ligands repel electrons in unhybridised d orbital of metal ion. The transition metal ion like Co +3 complexes exhibit many intense colours in host crystals or solutions.
The colour of light absorbed by complexed ion is related to electronic energy changes in structure of complex.
The electron leaping from a lower energy state to a higer energy state. If the crystal field strength is weak and the energy gap is small leading to unpaired electrons and form a paramagnetic complex in case of 4th and 5th electron going to higher energy d z 2 and d x 2 - d y 2 .
The fourth through 6 electrons will pair with d xy , d yz , and d zx . if the field is strong and the energy gap is large, leading to paired electrons and a diamagnetic complex
The colour of transition metal ion, Co +3 complexes differs depends on the coordinated ligands, which is due to change in electronic energy in the structure of complex while colour of particular lanthainde Eu 3+ (europium) exhibit similar pale pink clour this is due to f-->f transition rather than d--->d transition.
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molecular rearrangement introduction which includes nucleophilic, electrophilic, and free radical rearrangement. and mechanism, applications of favorskki and benzil benzilic acid rearrangement.
It consists of introduction about nano world and how it is different from the macroscopic world and what are the reasons. it gives information about silver nanoparticles antimicrobial property and it is various application. it consists of synthesis, characterisation of silver nanoparticles.
complexometric titration , colorimetry and spectrophotometry ushaSanmugaraj
it consists of notes for complexometric titration principle, edta, procedure, applications. colorimetry and spectrophotometry principle, introduction, instrumentation and applications
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
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Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
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.
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2. OXIDATION STATE
The total number of electrons that an atom either gains or loses in order
to form a chemical bond with another atom.
The underlying principle for oxidation state is conservation of mass.
Since electrons cannot be created or destroyed a proper accounting of
where electrons go is central to understanding chemical reactions.
It also determines the ability of an atom to oxidise (to lose electrons) or
to reduce (to gain electrons) other atoms or species.
If we assign oxidation states before and after a reaction, the we can
understand where the electrons flowed during the reaction.
Electrons are where all the action is in chemical reactions.
Oxidation results in an increase in the oxidation state and reduction
result in a decrease in the oxidation state.
3. LANTHANIDES
Rare Earth Element
Occurrence: 3×10-4 .
% of earth crust
Available in monzite
sand as lanthanide
orthophophates
Norwegain
mineralogist victor
Gold schmidt in 1925
Z= 58 to 71
Fifteen metallic elements
( La to Lu)
Highly dense elements
(6.1 to 9.8g per cc)
Mp: 800 – 1600
Bp: 1200 - 3500
Valance electrons lies in
4f orbitals
Electronic configuration
[Xe]4f1-145d0-16s2
4. All of the elements in the series closely resemble lanthanum and each
another in their chemical and physical properties.
They have a lustre and are silvery in appearance.
They are soft metals and can even be cut with a knife
The elements have different reaction tendencies depending on basicity.
Some are very reactive while some take time to react.
Lanthanides can corrode or become brittle if they are contaminated with
other metals or non-metals.
They all mostly form a trivalent compound. Sometimes they can also form
divalent or tetravalent compounds.
They are magnetic.
7. All the elements in the lanthanide series show an oxidation state of +3
Lanthanides show variable oxidation states. They also show +2, +3, and +4
oxidation states
But the most stable oxidation state of Lanthanides is +3. Elements in other
states hence try to lose or gain electrons to get +3 state
By that those ions become strong reducing or oxidizing agents respectively
Uneven distribution of oxidation state among the metals is attributed to the
high stability of empty, half-filled or fully filled f-sub shells
Ln, Pm, Ho, Eb, Lu +3
Ce, Pr, Tb, Dy +3,+4
Sm, Eu, Tm, Yb +2,+3
Nd +2,+3,+4
8.
9. Greater stabilization of the 4f orbitals compared to 5d and 6s
The order of penetration of the orbitals into the inner electron
core is 4f>5d>6S
The 4f electrons are the closest to nucleus and attracted by it the
most.
Now as successive ionisation increases the net charge on the
lanthanide cation being closest to the nucleus,4f electrons are
pulled even more closer than 5d and 6s electrons.
Thus is Ln3+,4f electrons are just too strongly pulled by the
nucleus to be ionised further as it requires huge energy for it
So states higher than +3 is generally not seen.
10.
11. OCCURRENCE OF +4 OXIDATION STATE
Ce4+ noble gas configuration
but it reverts to a +3 oxidation state and thus acts as a strong oxidant and can
even oxidize water, although the reaction will be slow.
Pr4+, Nd4+ Earlier in the lanthanide series
so the effective nuclear charge is not so high to be able to attract the 4f
electrons much more than 5d and 6s
Tb4+, Dy4+ (4f7 valence shell) Half shell effect
more stable than other filled orbitals.
Ce4+, Pr4+, Nd4+, Tb4+, Dy4+
12. OCCURRENCE OF +2 OXIDATION STATE
Eu2+ [4f7 ], Sm2+ [4f6 ], Yb2+ [4f14] clear influences of
electronic shell structure
Europium (Z=63) [Xe] 4f7 6s2 half-filled
4f7 configuration and hence it readily forms Eu2+ion.
Eu2+ then changes to the common oxidation states of lanthanides (+3) and
forms Eu3+, acting as a strong reducing agent.
Ytterbium (Z=70) fully filled f-orbital
It has similar reasons for being a strong reducing agent, in the Yb2+ state.
13. Oxidation state in Aqueous Solution
In aqueous solution, Sm2+, Eu2+ and Yb2+ loose electron, i.e get
oxidized and are good reducing agents.
On the other hand Ce4+, Pr4+, Tb4+ gain electron – gets reduced and
are good oxidizing agents.
Higher oxidation states (+4) of elements are possible only with oxides.
Example: Pr, Nd, Tb and Dy.
CONSEQUENSES OF OXIDATION STATES
Colour of the ions
Ionization energy
Lanthanide contraction
Separation of lanthanides
Basic strength of hydroxides
complex formation
14. COLOUR OF IONS
Lanthanides ions can have electrons in f-orbital and also empty orbitals like
the d-block elements.
When a frequency of light is absorbed, the light transmitted exhibit a colour
complementary to the frequency absorbed.
Inner transition element ions can absorb the frequency in the visible region
to use it for f-f electron transition and produce visible colour.
Many of the lanthanide metals are silver-white.
The lanthanide ions with +3 oxidation state
are coloured both in solid-state and in aqueous solution.
The colour of a cation depends on
the number of unpaired f electrons Lanthanides,
with xf electrons, have the same colour as of (14-x) electron elements.
15.
16. IONISATION ENERGY
Ionization energy Energy needed to remove the valence electron from
the atom/ion and is directly related to the force of attraction on the electron.
Across the periodic table,
Also, the ionization energy will be
more for half-filled and fully filled orbitals.
Atomic no: Nuclear charge: Size:
Ionization Energy:
17. LANTHANIDE CONTRACTION:
The atomic size or the ionic radii of tri positive lanthanide ions decrease
steadily from La to Lu due to increasing nuclear charge and electrons entering
inner (n-2) f orbital.
This gradual decrease in the size with an increasing atomic number is
called lanthanide contraction
The lanthanide contraction is the result of a poor shielding effect of 4f
electrons
Shielding effect the inner-shell electrons shield the outer-shell
electrons so they are not effected by nuclear charge.
POOR SHIELDING Positively charge nucleus decreasing the
has greater attraction to electrons atomic radius as the Z
Shielding effect: s > p > d > f
18.
19. SEPERATION OF LANTHANIDES
Since all the elements exhibit the +3 oxidation state as common,
they have similar properties
Thus, the separation of elements in its pure state is difficult.
BASIC STRENGTH OF HYDROXIDES
As the size decreases, charge to size ratio increase, the ionic character
decreases or covalent character increases making hydroxides les and less basic
More the charge to size ratio, the electron cloud of anion is more polarized,
more covalent character.
As the size of lanthanides decreases from La to Lu, the covalent character of
the hydroxides increases and hence their basic strength decreases.
Thus, La (OH)3 is more basic and Lu(OH)3 is the least basic.
20. COMPLEX FORMATION
Lanthanides exhibiting 3+ oxidation state is the larger and hence low
charge to radius ratio.
This reduces the complex-forming ability of lanthanides compared to d-
block elements.
Still they, form complexes with strong chelating agents like EDTA, β-
diketones, oxime etc. They do not form Pπ-complexes.
ELECTRODE POTENTIAL
Formation Ce4+ of is favoured by the noble gas configuration.
E0 value for Ce4+ / Ce3+ is +1.74 V which is enough to oxidize the water.
Thus the reduction potential ( tendency to accept electrons) is more
They act as a good oxidant and the reaction rate is slow
Thus act as a Good analytical reagent
