Lanthanoids Flashcards
What are the two series that make up the f-block?
Lanthanoids and actinoids
The f-block consists of the fourteen lanthanoids following lanthanum and the fourteen actinoids following actinium.
Which element is usually included in discussions of the lanthanoids?
Lanthanum
Lanthanum closely resembles the lanthanoids and is often represented by the general symbol Ln.
What general symbol is often used for lanthanoids?
Ln
Ln is used to represent the series of lanthanoids.
How do lanthanoids compare to ordinary transition elements?
Lanthanoids resemble one another more closely
They have only one stable oxidation state, which allows for examination of small changes in size and nuclear charge.
What complicates the chemistry of actinoids?
Wide range of oxidation states and radioactivity
The complexity arises from the variety of oxidation states and the special problems posed by their radioactivity.
What is the oxidation state characteristic of lanthanoids?
One stable oxidation state
This allows for a clearer comparison among the lanthanoids.
What are the key features of the actinoids’ chemistry?
Complicated due to oxidation states and radioactivity
The actinoids exhibit a wide range of oxidation states and their radioactivity complicates their study.
What is the common electronic configuration of the atoms mentioned?
6s
Atoms have variable occupancy of the 4f level.
What is the most stable oxidation state of all the lanthanoids?
Tripositive ions
This oxidation state has electronic configurations of the form 4f^n (n = 1 to 14 with increasing atomic number).
The electronic configurations of tripositive ions of lanthanoids are of the form _______.
4f^n (n = 1 to 14)
The variable occupancy corresponds to increasing atomic number.
What is the lanthanoid contraction?
The lanthanoid contraction is the overall decrease in atomic and ionic radii from lanthanum to lutetium in the lanthanoid series.
Q: What causes the lanthanoid contraction?
The lanthanoid contraction is caused by imperfect shielding of the 4f electrons, which leads to an increase in effective nuclear charge experienced by the outer electrons.
Q: How does lanthanoid contraction affect the M³⁺ ions?
The decrease in size of M³⁺ ions is fairly regular across the series due to the lanthanoid contraction
Q: How does lanthanoid contraction affect the M³⁺ ions?
The decrease in size of M³⁺ ions is fairly regular across the series due to the lanthanoid contraction
Q: What happens to nuclear charge across the lanthanoid series?
A: The nuclear charge increases along the lanthanoid series, contributing to the contraction in size.
Which elements exhibit almost identical radii due to the lanthanoid contraction?
Back:
Zirconium (Zr) and Hafnium (Hf) exhibit almost identical radii due to the lanthanoid contraction.
What series of elements does the lanthanoid contraction affect?
Back:
The lanthanoid contraction affects the radii of the members of the third transition series, making them similar to the corresponding members of the second series.
How does the lanthanoid contraction influence chemical separation?
Back:
The lanthanoid contraction makes the separation of elements with similar radii, like Zr and Hf, more difficult in natural processes.
Predominant oxidation states of Lanthanoids
La+² , La +³
Ocassionally __ and ___ in solution or solids occured
+2 and +4
Irregular in ionisation enthalpy arise due to
Extra stability of half filled
Empty
Completely filled f orbitals
Ce +⁴ configuration is ______and its strong oxidant or reductant reverting +³ common state
It can oxidise ____
Water
Ce+⁴ can oxidise water it’s good ___ agent
Analytical agent
Pr Nd Tb Dy exhibit ___ ox state only in Oxides MO²
+4
Pr Nd Tb Dy exhibit ___ ox state only in Oxides MO²
+4
Eu+² configuration tell
Is strong ______agent
4f⁷ 6s⁰
Reducing
Changing from +⁴ to +³ ox state
Eu+² configuration tell
Is strong ______agent
4f⁷ 6s⁰
Reducing
Changing from +⁴ to +³ ox state
Yb+² ox state is oxidant or reductant
4f¹⁴ 6s⁰
Reducing agent or reductant
Tb+⁴ is half filled it’s oxidant or reductant
Oxidant
Tb+⁴ is half filled it’s oxidant or reductant
Oxidant
Behaviour of Sm is like __
Eu exhibit both +2 and +3 ox state
Q: What are the physical characteristics of lanthanoids
Lanthanoids are silvery-white, soft metals that tarnish rapidly in air.
Q: What are the physical characteristics of lanthanoids
Lanthanoids are silvery-white, soft metals that tarnish rapidly in air.
How does the hardness of lanthanoids change with atomic number?
A: Hardness increases with increasing atomic number, with samarium being steel- hard
What is the melting point range for most lanthanoids?
A: The melting points of lanthanoids range between 1000 to 1200 K.
Which lanthanoid has a higher melting point, and what is it?
A: Samarium melts at 1623 K, which is higher than most lanthanoids.
What are the typical metallic properties of lanthanoids?
Lanthanoids have a typical metallic structure and are good conductors of heat and electricity.
Do the density & properties of lanthanoids change smoothly across the series?
: Yes, the properties change smoothly except for europium (Eu) and ytterbium (Yb) and occasionally samarium (Sm) and thulium (Tm).
Trivalent lanthanoid ions are coloured in ____ and aq state
Solid state
Why are many trivalent lanthanoid ions colored?
A: Their color is due to the presence of f electrons.
Why are many trivalent lanthanoid ions colored?
A: Their color is due to the presence of f electrons.
Which trivalent lanthanoid ions do not show any color?
: La³⁺ and Lu³⁺ ions.
Q: Why are the absorption bands of lanthanoid ions narrow?
A: Because the excitation occurs within the f level.
Q: Which lanthanoid ions are paramagnetic?
A: All lanthanoid ions except the f⁰ type (La³⁺, Ce⁴⁺) and the f¹⁴ type (Yb²⁺, Lu³⁺).
First IE of lanthanoids
And Second IE
600kJ
1200 KJ
Third IE abnormal low value for
For Ln Gd Lu
exchange enthalpy appears
In chemical behaviour early members are quite similar like ___ but with increasing atomic number behave like _____
Ca and Al
E⁰ values for
Ln³+ +3 e– Ln(s)
Except for Eu
-2.2 to -2.4 v
Eu -2.0 V
Q: What is formed when lanthanides (Ln) burn in oxygen (O₂)?
A: Ln₂O₃ (Lanthanide oxides)
Q: What is the product when lanthanides react with sulfur (S)?
A: Ln₂S₃ (Lanthanide sulfides)
Q: What is formed when lanthanides react with nitrogen (N) upon heating?
A: LnN (Lanthanide nitrides)
Q: What happens when lanthanides are heated with carbon (C) at 2773 K?
A: LnC₂ (Lanthanide carbides)
Q: What is the reaction product when lanthanides react with halogens?
A: LnX₃ (Lanthanide halides)
Q: What is formed when lanthanides react with water (H₂O)?
A: Ln(OH)₃ + H₂ (Lanthanide hydroxides and hydrogen gas)
Q: What do lanthanides form when they react with acids?
A: H₂ (Hydrogen gas)
They are basic like _____
Alkaline earth metal oxides and hydroxides
Q: What is the primary use of lanthanoids?
A: Lanthanoids are primarily used for the production of alloy steels for plates and pipes.
Q: What is mischmetal composed of?
A: Mischmetal consists of ~95% lanthanoid metal, ~5% iron, and traces of sulfur (S), carbon (C), calcium (Ca), and aluminum (Al).
Q: What are some uses of mischmetal?
A: Mischmetal is used in Mg-based alloys to produce bullets, shells, and lighter flint
Q: What role do mixed oxides of lanthanoids play in industry?
A: Mixed oxides of lanthanoids are used as catalysts in petroleum cracking.
Q: How are individual lanthanoid oxides (Ln oxides) utilized?
A: They are used as phosphors in television screens and similar fluorescing surfaces.
