what is lanthanide contraction what are the consequences of lanthanide contraction
Mohammed
Guys, does anyone know the answer?
get what is lanthanide contraction what are the consequences of lanthanide contraction from screen.
Define lanthanoid contraction and mention its consequences. JEE Chemistry Q&A
Define lanthanoid contraction and mention its consequences. Find the answer to this question along with unlimited JEE Chemistry questions and prepare better for JEE 2020 exam.
Byju's Answer Standard XII Chemistry
Size of Atoms and Ions
Define lantha... Question
Define lanthanoid contraction and mention its consequences?
Open in App Solution
Part 1: Lanthanides:Lanthanides are the inner transition elements of the modern periodic table i.e. the elements with atomic numbers from 58 to 71after the lanthanum(La).
They are also called rare earth metals because they are very rare on earth.
Part 2: Lanthanide Contraction:The steady decrease in the atomic size of lanthanides on increasing the atomic number is due to the increasing the nuclear charge and electrons entering the inner
(n-2)f
orbital or anti penultimate shell. This steady decrease in the size with an increasing atomic number is called lanthanide contraction.
Part 3: Consequences of Lanthanide Contraction:Atomic size:The size of the atom of the third transition series is closely the same as that of the atom of the second transition series. For example, the atomic radius of
Zr=
atomic radius of Hf and the atomic radius of
Nb= atomic radius of Ta etc.
Difficulty in the separation of lanthanides:As there is only a minute change in the ionic radii of lanthanides, their chemical properties are the same. This makes the separation very difficult.
Effect on the basic strength of hydroxides:The size of lanthanides decreases from
La to Lu
, the covalent character of the hydroxides increases, and hence their basic strength decreases. For example,
Lu(OH)3
is said to be the least basic, and
La(OH)3 is more basic.
Complex formation: Due to the smaller size but higher nuclear charge, the tendency to form a coordinate compound.Complexity increases from the element
La3+to Lu3+ Suggest Corrections 121
SIMILAR QUESTIONS
Q.What is lanthanoid contraction? What are the consequences of lanthanoid
contraction?
Q.What is lanthanoid contraction? What arc the consequences of lanthahoid contraction?
Q. What is meant by lanthanoid contraction? The actinoid contraction is greater than that of lanthanoid contraction. Why?Q. What is Lanthanoid contraction? Mention one of its consequences.Q. What is lanthanoid contraction ? Mention 3 consequencesView More RELATED VIDEOS
Atomic Size CHEMISTRY Watch in App EXPLORE MORE
Size of Atoms and Ions
Standard XII Chemistry
Lanthanoid Contraction
Learn about lanthanoid contraction topic of Chemistry in detail explained by subject experts on vedantu.com. Register free for online tutoring session to clear your doubts.
Lanthanoid Contraction
Chemistry
Lanthanoid Contraction
Download PDF NCERT Solutions
Popular Textbook Solutions
CBSE ICSE State Boards Competitive Exams Important Concepts Other
What is Meant by Lanthanide Contraction?
Last updated date: 12th Mar 2023
• Total views: 207.6k • Views today: 1.88k
Lanthanoid contraction definition - In Chemistry, lanthanoid contraction, also called lanthanide contraction, occurs as the atomic size or the ionic radii of the tripositive lanthanide ions steadily decrease from La to Lu because of the electrons entering the inner (n-2) f orbitals and the increasing nuclear charge. This particular gradual decrease in the size with an increasing atomic number is referred to as lanthanide contraction.
Lanthanide contraction happens to all the 14 elements that are present in the lanthanide series. Cerium(Ce), Praseodymium(Pr), Neodymium(Nd), Promethium(Pm), Samarium(Sm), Europium(Eu), Gadolinium(Gd), Terbium(Tb), Dysprosium(Dy), Holmium(Ho), Erbium(Er), Thulium(Tm), Ytterbium(Yb), and Lutetium(Lu) are the total elements that are included in the series. In accordance with the lanthanide contraction of the mentioned elements, as the atomic number increases, the atomic radius of these elements decreases. This is very easy to compare by taking into consideration Ce and Nd in the periodic table. Ce has the atomic number 58 and Nd has the atomic number 60. Now, look at the graph below to find out the atomic radius of the following elements mentioned above.
(Image will be uploaded soon)
About Lanthanide Contraction
Lanthanide contraction is the steady decrease in the size of the ions and atoms of the rare earth elements with increasing atomic numbers from lanthanum (atomic number 57) to lutetium (with an atomic number 71). For every consecutive atom, the nuclear charge can be more positive by a single unit, accompanied by the corresponding increase in the electron count present in the 4f orbitals surrounding the nucleus.
The 4f electrons imperfectly protect each other from the increased positive charge of the nucleus, resulting in a steady rise in the effective nuclear charge attracting every electron as the lanthanide elements progress, resulting in successive decreases in ionic and atomic radii.
Consequences of Lanthanide Contraction
The following points will depict the effect of lanthanide contraction more clearly.:
Atomic Size
The size of the atom of the third transition series is approximately similar to that of the atom of the second transition series. For example, the radius of Zr = radius of Hf and the radius of Nb = radius of Ta, and so on.
Difficulty in the Separation of Lanthanides
As there is only a small change in the ionic radii of the Lanthanides, their chemical properties are the same. This makes the element's separation in the pure state difficult.
Effect on the Basic Strength of Hydroxides
As the size of the lanthanides decreases from the elements La to Lu, the covalent character of the hydroxides increases, and thus, their basic strength decreases. Therefore, Lu(OH)₃ is said to be least basic, and La (OH)₃ is said to be more basic.
Complex Formation
Due to the smaller size and higher nuclear charge, the tendency to produce coordinate. Complexity increases from the element La³⁺to Lu³⁺.
Electronegativity
It increases from the elements La to Lu.
Ionization Energy
Electron's attraction by the nuclear charge is higher, and thus the Ionization energy of the 5d elements is much larger compared to 4d and 3d. In the 5d series, the total elements except Pt and Au contain a filled s-shell.
Elements from Hafnium to rhenium contain similar Ionization energy, and after that, the Ionization energy increases with the number of shared d-electrons such that Gold and Iridium hold the maximum Ionization Energy.
Case Study
Mercury - the Liquid Metal
At room temperature, mercury is the only metal that remains in its liquid form. The nucleus pulls the 6s valence electrons very close together (due to lanthanide contraction), making the outer s-electrons less involved in metallic bonding.
Formation of Complex
Lanthanides with a 3+ oxidation state have a higher charge to radius ratio and hence a lower charge to radius ratio. As compared to d-block elements, this decreases the ability of lanthanides to form complexes. Still they form complexes with strong chelating agents like EDTA, β-diketones, oxime, and so on. They do not form Pπ-complexes.
Cause of Lanthanide Contraction
The effect of lanthanide contraction results from the poor shielding of nuclear charge (with the attractive nuclear force on electrons) by 4f electrons; the 6s electrons can be drawn towards the nucleus, hence resulting in the smaller atomic radius.
In the case of single-electron atoms, the average separation of an electron from the nucleus is defined by the subshell it belongs to and decreases with an increased charge on the nucleus, where this, in turn, leads to the decrease in atomic radius. Whereas, in the case of multi-electron atoms, the decrease in the radius brought about by an increase in nuclear charge is partially offset by the increasing electrostatic repulsion among the electrons.
A "shielding effect" operates, in which existing electrons shield the outer electrons from the nuclear charge by causing them to undergo less effective charge on the nucleus as more electrons are applied to the outer shells. The inner electrons' shielding effect decreases in the following order: s > p > d > f.
Lanthanoid Contraction and Its Consequences
Lanthanide contraction is the constant reduction in the size of the atoms and ions of the rare earth elements as their atomic number increases, beginning with lanthanum (atomic number 57) and ending with lutetium (atomic number 71)
Lanthanoid Contraction and Its Consequences
Lanthanide contraction is the constant reduction in the size of the atoms and ions of the rare earth elements as their atomic number increases, beginning with lanthanum (atomic number 57) and ending with lutetium (atomic number 71)
TABLE OF CONTENT
Properties of lanthanides
Lanthanide Contraction
Reasons for Lanthanide Contractions
Lanthanides are the modern periodic table’s rare earth elements, with atomic numbers ranging from 58 to 71 after lanthanum. Since the occurrence of these elements is extremely uncommon, they are known as rare earth metals.
The lanthanide series is the set of elements in which the 4f sublevel is full. All of these elements are metals (specifically, transition metals). They share several characteristics.
However, there is significant disagreement over where the lanthanides begin and terminate. Lanthanum and lutetium both are d-block elements and not f-block elements. Nonetheless, the two components share features with the other elements in the group.
When addressing generic lanthanide chemistry, the lanthanides are denoted by the chemical symbol Ln.
Lanthanides are a part of lanthanide series, rare earth metals are a part of rare earth elements
Inner transition metals and lanthanoids are all names for this group of elements.
Properties of lanthanides
Physical qualities are similar across the series.
Adoption of the +3-oxidation state is the most common. They can also have an oxidation state of +2 or +4, while some lanthanides are most stable in the +3 oxidation state.
Adoption of coordination numbers larger than six that is around eight to nine in compounds.
Across the series, there is a tendency for the coordination number to decrease.
A tendency of binding towards elements that are more electronegative (such as O or F)
There is less reliance on ligands.
Rapid ligand exchange occurs in ionic complexes.
Lanthanide Contraction
As nuclear charge increases and electrons reach the inner (n-2) f orbitals, the atomic size or ionic radius of tri positive lanthanide ions decreases progressively from La to Lu. Lanthanide contraction refers to the consistent reduction in size with increasing atomic number.
The atomic radius trend seen in the Lanthanide series is described by this contraction. It is a crucial phenomenon in defining the properties of lanthanide series elements.
The Lanthanide Contraction holds true for all the 14 elements in the Lanthanide series, they are-
Cerium(Ce), Praseodymium(Pr), Neodymium(Nd), Promethium(Pm), Samarium(Sm), Europium(Eu), Gadolinium(Gd), Terbium(Tb), Dysprosium(Dy), Holmium(Ho), Erbium(Er), Thulium(Tm), Ytterbium(Yb), and Lutetium are all members of this series (Lu).
According to the Lanthanide Contraction theory, the atomic radius of these elements decreases with a gradual rise in their atomic number .
Reasons for Lanthanide Contractions
Lanthanoid contractions occur as a result of the failure of the f orbit shields to balance the growing charges with the increased amount of atoms, resulting in the contractions.
Since nuclear charge exists in the inner shell of electrons, the job of shielding here is straightforward: it protects the outer shell from the charges of the inner shell.
The shields in f-block elements fail to protect the outer shell from the nuclear charge, implying that positively charged particles enter the outer shell.
When positively charged particles and electrons interact, the atomic radius decreases as the number of atoms increases.
Causes of Lanthanide Contraction
The interaction of positive nuclear charge with the outer shell of the orbit, resulting in electron compression.
The number of atoms in the elements grows.
The 11 electrons’ inability to shelter 4f electrons from 5s2, 5p6, 5d1, and 6s2 subshells and shells.
Weak shielding effect of the various components of 4f block elements.
The interaction of all the elements of the 4f block with a positive nuclear charge has a cumulative impact, thus resulting in a bigger contraction in the 4f block elements
There is an abrupt contraction of the periodic table elements 57-58, due to the above mentioned phenomenon.
Consequences of Lanthanide Contractions
The major consequences of Lanthanide Contractions are as follows: –
Atomic size –An atom in the third transition series is roughly the same size as an atom in the second transition series. For example, the radius of Zr equals the radius of Hf, and the radius of Nb equals the radius of Ta, and so on.
Difficulty in the separation of lanthanides –Lanthanides have chemical properties that are comparable because their ionic radii differ just a little. In the pure form, this makes element separation difficult.
The influence of lanthanide size on the basic strength of hydroxide –As the size of the lanthanide decreases from La to Lu, the covalent nature of the hydroxides increases, hence their basic strength decreases.
As a result, La(OH)3 has higher basicity, whereas Lu(OH)3 has the lowest basicity.
The reason to generate coordinates is a result of the smaller size and enhanced nuclear charge. From La3+ to Lu3,
Guys, does anyone know the answer?